I think you would waste less time by sticking with Xcode rather than looking for another IDE if you want to develop for the Mac (or iPhone).
Apple made a lot of effort to kill any competitor in that area to make sure any developer wanting to develop for the Mac platform use Xcode and only Xcode.
It might not be the best IDE but it does work well and it is the IDE developers at Apple are using. Somehow it does its job. The frameworks and the documentation are very well integrated.
I use TextMate a lot and also SubEthaEdit but they are not full IDE as you’ve described above.
Best Regards.
