I think the iTunes app store is a lot more established than anything Android could offer at this point, but it seems like it's growing a lot, especially with all the buzz around the Droid and Nexus One
The apps that I'm going to get are the aforementioned At Bat (listen to baseball games from the home or away radio feed, over your phone), the barcode scanner, locale (your phone has different settings based on where you are - vibrates at work, loud at somewhere else, etc), and a few various apps for productivity, since it is a work phone and all.
I'd be interested in games, but I haven't heard of any that sounded too good. My wife has Oregon Trail, which was really entertaining for about 5 minutes, but that was all.