First of all, I'd like to say that i LOVE the file scopes. It's great to see all those colors when I've got 10 or so files open and i love colors.
However, I'm working on a team of about 10. We have a models folder that's broken down into documents, tools, etc. I'm not real sure why these separate models aren't in their own folders. However I can't simply use a full regex to say I want the files in the models folder that end in _document.rb to be in this scope and the ones that end in _tool.rb to be in this other scope. Really, these files need to be in their own folders, but it's going to be hard for me to argue "hey guys, we should restructure our whole project so I can get these pretty colors to show up in RubyMine". Especially since most of them are de facto TextMate users (i'm working on converting them and it's going well so far).
However, until then, it'd be cool to have full regex's in scopes. I don't know if it's too late to bring this feature in, considering it's minor and you guys have already gone in another direction.