I'm liking development in XCode. Tools are so intuitive. OCUnit is built into XCode, with near identical syntax to other XUnit frameworks. HW simulation available which while obvious, isn't always done well for many devices. I'm not sure the arguments of a 'closed platform' hold completely against Apple; they have made it very simple to develop apps, and if you want your app available for your enterprise only, you can do that (it seems). Sure, it's filtered.
I'm keen to look at Android. It's obviously easier to get tools out there, so I'm eager to see the maturity of the dev and unit test tools themselves.
