Yesterday I configured <CR> to run RSpec with the current file in a separate tmux session and window, and I'm never going back!
Plus I somehow managed to speed up RSpec a bit using bundler --standalone and spring and stuff.
I'll put it up on my blog sometime this week. It's too good not to. (And no, this is nothing new, it's been out there for a while, but now it works for me, too. :D )