EDIT: Tried installing the new version of Yi out of curiousity, maybe they made optimizations or my computer is now fast enough, but as of now it seems more than responsive enough. You can run Yi with Vi or Emacs keybindings.And maybe, just maybe, someone will succeed in the gargantuan effort to create a usable replacement for Emacs in some other high-level language. Probably not any time soon, I'd bet.
It's kinda a shame, I love the idea of a completely transparent configureable editor. I tried Yi a while back, an editor written in Haskell, and it was uncomfortably slow to use/could use optimization. As languages become more expressive, we may see more projects like it.
How did you get Yi to install properly? I was unable to get several dependencies to install (notably gtk2hs) on Linux Mint 15. I couldn't even get vty to install! I don't know if it was cabal or Hackage or whatever, but I spent hours on the installation, and no way I tried worked. EDIT: Also, I suspect that perhaps the reason it was formerly extremely slow is because they used to use a Haskell interpreter, and now they use a compiler.
Yi's performance has improved considerably. But it doesn't really do enough to use as your editor [ at least for me ]. I love xmonad; beautiful code and wonderful program. The Yi team seemed to aim for a great deal of the good things in Xmonad, but development slowed. I'm on Arch, but I find haskell programs -- it's my main language -- best with cabal. I.e. for you on Mint, I would just install your ghc package and your cabal-install package then install all other haskell programs with `cabal`. Now that it has sanboxing you may not need [ but certainly may use ] cabal_dev or hsv_env. I had a (the same?) gtk2hs error when using the arch packages for much of my haskell environment. Problem went away when moving to Cabal.
I think Yi could be spectacular ; especially as Haskell is so suited to language parsing. You could get things like what Emacs Semantic mode wants to be, only, um, actually work.
edit: i accendtly a word and there was some unwanted formatting