Your comments

There's another report for getting a preference option in to disable animations. Vote on that one I'd say. :)
In 20110203 this keybinding is already present.
That or use CTRL-W, which is why I do to close tabs. I almost never use the close button, so reclaiming that space would be worthwhile.
Confirmed on my Win7 x64.

Stops using the foreground colour after column 512.
The problem is that a large part of ST itself uses Python to do all kinds of things. So the interpreter and the editor are rather tied together. Like Denis said, the best way forward is to write a plugin that embeds the IRB.
Sounds like you're on OSX?

I have not encountered this on Windows 7 at least.
What platform? Because it changes from pointer to text for me on Windows 7 if I move the mouse pointer from the menu/tabs to the editor window.