My favourite new feature in Vim 7.4 has got to be case-insensitive tab-completion for filenames. I've had it in bash for years and my fingers got lazy, tripping me up every time I opened a file from inside Vim. No longer!
Yurk, case-sensitive completion is the only think that keeps me sane!
Yeah, I was pretty happy on finding iswitchb-mode in Emacs, being likewise case-insensitive.
I really do wish T&R had used OSX-style file name semantics in 1st Ed. though — this would have had to have been the default behaviour for apps from the get-go.