I would love to use a different editor than XCode for coding, but I feel, that no other editor integrates tightly enough with it to be really worthwhile.
However, given some time, TextMate might eventually get to that point. At the moment though, it primarily lacks debugging features and refactoring.
For everything that does not need XCode, I love TextMate. If I had another Mac-user in my workgroup I would probably consider SubEthaEdit for its collaboration features. If it is Emacs you want, I would recommend Aquamacs (more Mac-like) or Carbon Emacs (more GNU-Emacs-like)