Folding wherever I want, not wherever editor allows (i.e. not limited to blocks defined by syntax). Using Perl scripts in the same way as other commands. Passing the current file through awk. You have plugins for NetBeans or Eclipse, where I don't even need to think how to enable that -- I just run an external command. Quick and easy (no mouse) splitting window to see three or four files at the same time (or other fragment of current file). And many others that I take for granted, so they don't come to my mind at the moment.

Emulating vi keybinding is great and all, but that only scratches the surface. A big reason people like vim is the extensibility. I don't think that there is a single vi user(not necessarily a power user, but someone who uses vim for more than just editing a value in a config file) who doesn't have a single plugin installed.