I do a bit of work on the fringe of the Ruby community, and the Mac is popular there along with an IDE or two. However I’m beginning to see a few articles to the effect that the IDE is getting in the way after a point and that reverting to your favourite text editor as an IDE is actually more productive.
For old-farts like myself that would be VI (or VIM). Such a comment will probably bring cries of derision, more so than the idea of an editor replacing an IDE. But after a few decades editing is no longer a conscious act. Just as some people touch-type and the words appear on the screen (or paper) without any thought about the mechanics, so too with your favourite editor – only it extends to the non-alphanumeric keys too.
Of course I cheat; VIM has panels and Linux has all these windows and other things that make VIM usable as an IDE. Integrated? Yes, in my head. Its the best place for it.