As a long-time vim user I just recently made the switch to Emacs + Evil because of the excellent functional-language support Emacs has (with the slime plugin).
Vim users are used to the "modes" like insert, normal, visual. Coming from Vim it feels like Emacs is only in Vim's insert-mode. Having to press ctrl+key just to navigate the screen felt completely wrong to me. All the ctrl/alt keybindings just seems like a recipe for RSI.
However, with the Evil plugin, a Vim user can immediately use Emacs because you're editing with Vim keystrokes. Vim also encourages you to spend as little time in insert-mode, and there are very few commands in Vim that work in insert mode (to be honest, I never use them anyway)
So what you can do is you can tell Evil to drop Vim keybindings when you're in insert-mode (except for ESC) and then.. voila... you're back to Emacs keystrokes, but only while you're in insert-mode (which is what Emacs seems to be about anyway)
;; use Emacs keybindings when in insert mode }:)
(setcdr evil-insert-state-map nil)
(define-key evil-insert-state-map [escape] 'evil-normal-state)
This is the coolest thing ever if you want to learn both editor's commands, or if you're coming from the one/going to the other. (Yeah you can switch mode with Ctrl-z but this is "seamless" for a Vim user)
You probably also want the Evil-leader plugin so you can map things like ",f" to find-file and ",h" for help-command, etc.
In addition to those jbeja mentioned, there is also fiplr[1], somewhat in the spirit of ctrl-p, command-t etc. for vim.
One favorite tweak of mine for file finders like this in general: rewrite the dir listing to use "git ls-files -co --exclude-standard". This obviously only works in git projects (similar commands exist for mercurial I think), but is really fast and most of the time is exactly what I want.
vim emulation frustrates me to no end because it is never a complete emulation. Additionally, in emacs, there are many conflicting keybindings that prevent normal usage of using vim.
