I keep coming back to TextMate, not because it does anything intelligent with my python code but just because it's fast and simple. For some reason the speed of the text editor makes a big difference to usability.
For the past few years I've purchased Komodo IDE which has great features but the editor is infuriatingly sluggish, to the extent that often when I try to select some text it misses the beginning of my selection or fouls it up in some way. With every update I hope they'll have addressed this and I'm not alone in being frustrated by the editor.
It's time to look again at Eclipse and the news is good. The widgets (SWT) have been ported to Cocoa and this means that in the latest release, 1.5, no Carbon is required and I understand this means the future is bright for Mac users upgrading to Snow Leopard in August.
PyDev also supports Google App Engine projects which will be interesting to try out.
Eclipse "Galileo", version 3.5, looks really great and runs very snappily on my lovely new laptop.
BBEdit is my choice for manipulating large text files, TextMate quickly became a favourite and I look forward to what ever Allan Odgarrd is up to with version 2, but until then I'll live in Eclipse for a while.
It's a great time to be a developer working on the Mac platform.