I've done it recently and it wasn't too bad, with the help of rvm. Getting the entire ecosystem (git, heroku, postgres, etc...) running is a bit more work, but pretty straightforward.

Perhaps part of the confusion is that there are a number of old blog posts that you'll dig up via google, and if you make the mistake of following an older one, you'll run into problems. I made this mistake trying to get rails set up on Ubuntu before I knew about rvm, and it was pretty painful.