First of all, AI is NOT just for women and gays. I know several straight guys that are hooked on the show as well. :o)
My theory on why Kevin is there is b/c the judges (mainly Paula and Randy) keep playing up how "cute" he is and how everyone just wants to squeeze him. As Simon said on Larry King the other day, America is turning it into a popularity contest.
I think Ace CAN sing, but last week sucked. My top pics (from best to worst) are Katherine, Taylor/Chris (tied for me), Paris and Ace.