The reason I ask is I'm currently developing an Android app (as I have an Android phone and no mac) but I keep wondering if it's worth getting hold of a mac and iPhone sooner rather than later.
Android users simply don't buy as many apps, and the pretty steep upper limit on app sizes mean several apps you can easily do on iOS are considerably harder on android. We've yet to see a project yet where android outsells iOS. (This very likely has to do with the wonky payment system for Android which started with very few nations and still isn't anywhere near Apple's numbers of participating nations. For Most non-US specific apps, they sell about 50% abroad 50% domestic, so that's a HUGE deal.)
The tools have a laughable difference in quality (XCode/InterfaceBuilder used to be a little sketchy for apps, is now pretty good, but eclipse is still eclipse, and graphical layout and editing is still very out there for android, but is the norm for iOS).
(I used to be an embedded Linux dev, I really wish android was doing considerably better).
That $1289 you'd spend buying a late generation iPod Touch and a white macbook is very worth it (or a mac mini even).