Taking gel's w/ sports drinks...

I think most gels recommend using water.  Gu says that you can use their Gu2O sports drink with their gels and I have tried this with no ill effects.

I use Gu with Gatorade all the time...it seems to have no ill effects on me. I probably under-hydrate and under-eat during a long event, so maybe it's a good thing.

Gel + sports drink = too many carbs at once.  You're better off carrying 2 bottles with plain water in one for washing down gels and other solid fuels.

All the articles I've read recommend water with gels. They also recommend not to mix your intake on a race (if you do gels, just do gels. If you do sports drinks just do that).
The important thing to consider is the dilution ratio. The amount of electrolites / minerals / carbs / proteins etc per ounce of water. It is important for you to find out what is the right amount for you. If you overload your body you will be in as much trouble as not fueling your body enough. Training is the perfect time to start testing fuel types.
Also, If you do not drink enough water with your gel it will sit in your stomach and your body will not be able to absorbe the nutrients.
Everyone has different requirements and tastes. I prefer gels for races, I also use them in my long workouts.
- They are easy to carry, I do not have to depend on the race sponsor or location of the food station. Water stations are easier to come by. I plan my gel intake around water stations.
- The mix of sports drinks at races vary depending on the person that mixed them. I rather depend on my own mix, I hate water down sports drinks (or lemon gatorade which seems the one you always find at races).