After owning both an iPhone and an Android, it makes me wonder, is there more to a mobile OS than just launching applications? The thing I like about Android is that you can kind of piece your own Android system together, including the wonderful ability to choose an alternative home screen. In addition, when you press on, say, a Market link in the Browser, it takes you straight to the Market app and you can then press the Back key and go back to the Browser app, almost like they were just two different pages on the same app. iOS (<=4, at least) is much more....I dunno how'd you describe it, single-tasked? The OS part of it is pretty distinct from the applications; you browse around and then go into one application, then you have to leave to go to the next. Clicking a link in an e-mail zooms you out and switches you over to Safari, then you have to go back to the homescreen (or use "multitasking") to get back to the e-mail app.
Basically it just seems like Android is much more fluid, that everything is connected, and that you just glide from one application to the other. I'm definitely not saying that Android is not at all like iOS or that it is better because when you stop and think about it, that really is kind of what an OS is, especially a mobile one. It provides the base so that you can launch applications, and on mobile phones this is especially true. The only observation I'm making is that it just seems like iOS seems more strict in how it runs.
*shrugs* I dunno, random thought I had a while back. Let me know what you think about it.