You really have to try different brands and flavors to find what works. It seems to be very personal. I have friends who can't use gels, and instead eat chewable gummies instead (one swears by straight gummi bears, others use the Gu and PowerBar prodicts).

Personally, I've switched to mostly liquid nutrition, currently using a custom blend from Infinit. For 6+ hour races, I'll supplment with a PBJ sandwich or a bar of some sort.