Otherwise it really doesn't improve on a text editor. All of these things would require a ton of work, so I stick with Sublime for now. Text isn't that bad.
IDEs are kinda close, but I've yet to see one that could effectively work with dynamic languages. RubyMine is interesting-looking, but seems to want to impose a lot of its opinions on your workflow. I don't really see how RubyMine would really be that much better than Sublime and a terminal.