Di2

I can see the benefit for TT or triathlons...shifting on the drops, but don't see the benefit with road bikes.  Especially given the cost. 

yeah- those mechanical shifters never have problems. 

I bit the bullet and got a felt B10 with Di2.  Di2 would be a nice convenience for a road bike, but the difference it makes on a TT bike is exceptional.  Firstly- dual position shifting makes your TT bike suitable for group rides and even hill climbs.  Secondly, when in aero- you never hesitate to shift chainrings and 2 or 3 on the cassette all at the same time.  it's just beautiful how wonderfully it works. 

I've never hesitated to shift while in aero with regular shifters, front or rear.  2 or 3 at a time on the rear, no problem.  I really don't see how electronic shifting is any better.  I'm actually curious now -- can you explain exactly how Di2 is better?  From what you've stated so far I see no difference.

Shifting under load is huge if you're climbing or sprinting.

I may not have a need, but Im getting in non the less.  I have a 2012 Roubaix with Ultegra and since the day I have taken it home it has shifted like crap.  The shop and specialized has done everything in their power to make it shift right, but it never lasts, usually less than a month.  Both the LBS and Specialized got tired of the bike, and offered to warranty the cost of the groupset, and I have to pay the difference of what Specialized gives for the set up.  So for  $600 I am getting DI2.  

That being said, I also have seen all the problems the Tour riders are having and now an having second thoughts.  I hope it works out well, because honestly, I am sick of this bike not working right.  

ROY

Great.  Glad you enjoy your bike.  Ride the hell out of it and have fun.  You obviously don't need to spend the ridiculous amount of money it takes to get the pushy button thingies.  The only real difference for you would be the dual-position shifting.  If you use your bike in aero all the time, then it would have minimal value.

I was actually hoping you might explain something about Di2 to me, but I guess you don't feel like it.

So I'm guessing this Dual Position shifting means there are shifter buttons on the aero bars as well as on the bullhorns?  If so, that sounds kinda cool.  Probably not worth it to me personally, but sounds like a cool idea nonetheless.

How does Di2 help with shifting under load?  In my experience, problems with shifting under load have less to do with the shifter and more to do with the chain.  If I'm trying to upshift on a hill I try to take some pressure off the chain through the pedals before I make the shift.  I can see during a sprint it would help quite a bit by not having to move your hands much.  But I don't see how it helps with the shifting under load problem.  I've never had an issue downshifting under load, but then again I've never sprinted like a pro cyclist and put that kind of torque on a bike

Didn't Sagan or Griepel miss a sprint a few stages ago because of a chain issue, presumably from shifting under load (using Di2)?  I'm speculating here, but that's what I seem to remember from watching the end of that stage.  My memory is often not very good, as my wife will attest. 

I have Di2 on my TT bike and think it's great. I don't notice a difference shifting under load, but possibly because I don't do it very often or never had an issue on my road bike either. Shifting on the horns was the key reason I got it (and because it's really cool).

We don't know that the shifting issues people are having in the TdF are due to Di2, it's all been speculation. I think if people were having issues with it, we would know by now. People were riding with Di2 last year (and the year before I think), and I don't recall any issues coming up. I've never had an issue with it on my bike. Don't forget Campy also has an electric groupo now (not sure if it's released yet but I wouldn't be surprised if their pros are using it). If there are issues, it could also be on the campy set.

sorry- didn't mean to blow you off.  just didn't want to sell you on something that you didn't need or really want.  I don't find much if any different regarding shifting under load.  I really think the biggest advantage for a TT bike is the dual position capability.  Other than that- just how easy it is to shift when you're in aero.  Some of the aerobar shifters- like the DuraAce ones, are kinda stiff.  you really need to move your hand and forearm to shift.  Touching buttons is just- well, really easy so I find myself shifting more and more often.  And every shift is perfect.  Never need to wonder or worry.

The Di2, since it has no cables, tends to stay in adjustment- like forever.  And the battery lasts a LONG time.  they say 1000 hours, but many have gotten 3000 hours of riding out of it.

I do not have Di2 nor have I test ridden it.  But I too would like to have it, just not worth the cost to me at this point....because frankly, it's not enough better to warrant the price premium.  But that said, there are nice benefits to it... (btw, all the same things can be said about carbon frames, expensive wheels...the cars we drive...)

For one, one of the biggest issues with TT shifting is now that we are at 10 speeds and going to 11 speeds, the spacing of the cogs is getting so tight, especially with short chainstays on tt bikes that you always have to trim that front derailleur.  Di2 does that for you in each gear magically.

Also, TT shifters don't have any 'over-shift' built in to them.  Unlike road shifters you can push to the click, then a little further to help the chain catch the ramp.  So with Di2 the 'over-shift' is built in and you don't have to shift up 2, down 1 like I always have to do with my TT shifters.

I also hear that the electronic shifts are quicker and more positive than when we are actuating a cable by hand.

"I do not have Di2 nor have I test ridden it... I also hear that the electronic shifts are quicker and more positive than when we are actuating a cable by hand."

I've ridden four different versions of Shimano Di2 on several platforms using both road and time trial configurations and also ridden some custom wiring harness set-ups assembled by Jack Johnson and Mark Lee, both Shimano certified Di2 technicians.

My take on Di2, and I sense this would be easy to time with a shooting chronometer, is Di2 is noticeably slower in nearly all shift combinations. That said, it is almost certainly more "positive" or produces a more repeatable result.

I absolutely agree with the assertions that the front shifting from small ring to large and the auto-trim feature for chainline are excellent- mostly with specific respect to repeatability. It is, however, not the exclusive result of electro-mechanical actuation. A big, and frequently overlooked, feature to Di2 and better front shifting is the hoolow-forged crank and chainrings. They greater improve front shifting, especially from small ring up to large.

Finally, for the triathlete who is a good bike handler, the dual-control placement of the shifters on an aero cockpit is such a profound advantage it is unfair to those who don't have it. It is easy to guesstimate how much faster a rider would be by being able to shift to the perfect gear in all instances from both the base bars and the aerobars. The time savings for an experienced rider would be significant, I'll suggest tantamount to the very largest aerodynamic savings from using a disk, an aero helmet, etc. For the aero cockpit Di2 is a game changer. For the road bike... Meh...

I really dislike that I can not shift my road-bike when I am using my clip-on aero bars.

Di2 could fix that for me.

So I already decided that I will not buy a Tri-Bike or new Roadbike unless it has electronic shifting.

This beeing said I also hope that SRAM will come out with an electronic shifting and with all 3 companies offering that technology prices will drop.

It's easy to estimate that?  How?

i'll concede that I live in a relatively flat state, but the average TT doesn't even require that much shifting, let alone while on hte base bars.

"It's easy to estimate that?  How?"

Measure the time it takes to move your hands from the base bars to the aero bars to actuate a shift. It doesn't have to be precise, and in the instance I did it on an indoor trainer, it was not. It resides somewhere south of 1 second and north of .7 second for a few trials. Not scientific, but still not utterly insignificant.

Count your shifts for 10 minutes in a race. I did this in the opening miles of the Maumee Bay Triathlon a number of years ago where I had the second fastest bike split of the day. I shifted- I can't remember how many times- but it was many more than I would have estimated. A number north of 5 shifts is certain, and it is a board-flat (albeit gusty) course.

Now, do the arithimatic.

Of course, on internet forums, the default response is to argue, "That's not scientific... that isn't a study... you have to use a wind tunnel, a Cray supercomputer, test 5,000 subjects in triple blind tests over a decade and I still won't accept the answer..." So be it. That's forums. They are about arguing ad nauseum well beyond the obvious.

But remember- I said "estimate", and that is a key word. If you do the arithmatic, then discount the finding by 50%, it's still worth noticing.

Thanks, that gives me a better picture of the whole system and how it works.  Seems pretty cool, but not enough for me to base a purchase decision on it.

The purchase decision gets easier as the price comes down.  Di2 has already moved into the Ultegra group, about $2k less than the Di2 Dura-Ace price point, as I recall.