TextMate
Since doing a Late Night Cocoa interview with Rob Rix and Allan Odgaard about using TextMate for Cocoa development I have been giving it go and I have to say its pretty darn good. The ObjC support works well and if your prepared to change the overall update settings from minor or major updates to cutting edge you get reasonable although definitely not complete code completion support.
The main trouble with TextMate is when you first start using it your not quite sure what It can do and how to do it. I recomend you look for the Objective-C Screenscasts on the TextMate website and that should keep you going. Of course when it gets released in a couple of weeks time you can always use the TextMate episode of Late Night Cocoa to get you started.
