I know some Python and I'm really impressed by the language's ease of use. From what I've seen of Objective-C it looks a lot less pretty, but it seems to be the lingua franca for Mac OS X development (which means it has better documentation). 
I'm thinking about starting Mac development - will using PyObjC+Python make me a second class citizen?
DO NOT ATTEMPT to avoid learning objective-C if you're going to write apps for the Mac.  The purpose of PyObjC and the other language bindings is to let you re-use existing libraries in your apps, not to let you avoid learning the native tools.
What are the downsides of using Python instead of Objective-C?