FWIW: I use XCode for all Objective-C development, TextMate for almost everything else, and BBEdit to open large files (IMO the single biggest area of weakness for TextMate). I've tried other editors, but 3 covers everything I need.
I tried to use Texmate like that for a while but ultimately, not having a sensible undo and the kind of sucky non-regex incremental search blew it for me.