This is it in a nutshell. The practical problems like ObjC aren't an issue for OS X, so there's no reason for them to be so for the iPhone. It's largely a similar environment.

And the more high-brow arguments about lock-in and freedom are true, but obscure the simpler point: sorry, but I'm just not interested in paying $99 and waiting on a list for months just to run a program on my own phone!

Android has the distinct and notable advantage of actually being a working target platform for the people who want to play with it. Apple will no doubt attract a few established developers to the iPhone, but all the cool stuff will be happening on Google's platform.