It's a good effort, but suffers from the usual problems of replicating Vim, ie lots of subtle changes and lots of missing functionality. Both of which wreak havoc with one's muscle memory.

Also, I found it really slowed things down (in RubyMine), sometimes updating just 1-2 characters a second in a big project (on a modern MBP).

I've gone back and forth, but generally I prefer Vim with Janus distro, albeit I miss a lot of cool things from IDEA.