An allergy to non oxynol 9 makes exposure feel like douching with batter acid. Trojan was the only brand I could find without the hideous stuff on it.
I realize the spermicide makes the birth control aspect more effective, but I really hate it.
Another up side to using condoms is it helps a man's staying power. It takes some women alot longer to have an orgasm, so its nice to help the man slow down a bit.
Once in a while a condom might slide off during use. I have no idea if this can be "fixed" as it might have to do with other lubricants used during sex, but overall, a good product.