Well, I'm not gonna call you insane, but I do disagree with you. I think the difference between 30 and 60 fps is not only there, but highly apparent. It's not just a visual thing either. Faster frame rates allow for tighter controls so it does directly affects gameplay.
This might not help my case since you guys can't really see a difference, but watch these two videos. One is in full 60fps and the other is from Youtube, which caps at 30 fps. There is a very clear difference for me. Make sure you have at least a 60 hz monitor though, otherwise you really won't be able to see the diff.
http://www.youtube.com/watch?v=bUfp7LvxNwU&list=FLvHtEkC1NPbdC7c1eCupsnQ&index=1http://gamersyde.com/stream_devil_may_cry_pc_gameplay_1-29276_en.html