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.
I just upgraded from a "modern" macbook pro (2008, aftermarket SSD) to a "modern" retina macbook pro that is maxed out. IntelliJ and RubyMine fly like the wind on this new machine. The old one was painful to use IntelliJ but you could live with RubyMine performance.
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.