I'm in the process of switching from vim to emacs right now. It's frustrating, although viper-mode takes a lot of the pain away, and to be honest I find it a really nice combination to have the vi editing modality readily available within the powerful framework of emacs. Remapping caps lock to Control has helped enormously.

The most notable thing is that emacs encourages you to live in it much more than vim. With vim, I would navigate around in the shell, open up a file in vim, edit, close, repeat. With emacs I'm finding that I spend more time just switching buffers instead of running back to the shell because emacs doesn't simply quit when I kill all my open files. There's always more buffers, so the app stays open and I tend to remain there.

I'm still in the process of getting up to speed with basic editing things, although I've found that the way it manages buffers and what it calls windows (what the rest of the world calls frames these days) is quite easy and quick to use, and I found myself able to navigate around in emacs fairly quickly. All in all, I'm not 100% sure I'll stick with it, but I'm happy so far and I know that I'm still getting over the hump to where I'll be truly productive with it.