Paul,
I am doing my first 1/2 IM in Utah as well. I have been training/experimenting with three different energy gels (Clifshot, GU, and Hammergel). I have found that Hammergel works the best for me. It is easy to digest and it doesn't upset my stomach at all. When I am on the bike, I usually mix Hammergel right into my water bottle. Since I am not a HUGE fan of water anyway, adding the hammergel sort of makes the water taste like Propel (At least that's what I tell myself). When I run, I usually just carry the squeeze bottle full of gel. Either way, the gel is really easy to take in.
The nice thing about GU is that it will be available at the aid stations (they are a sponsor). It couldn't hurt you to try GU while training. If it does upset your stomach, it's better to find out now than on race day.
The website for hammergel is
www.hammergel.com You can order almost everything from their website. However, if you call them, you can buy the individual packets of hammergel. The packets are nice because you can get several different flavors and see which one you like the best. If you call in or go online, you can use coupon #39306 for 15% off your first order.
See you in Utah!
Craig