Have you tried Windows Phone? I'm a bit biased, I spent 3 years working on it, but I'll say that of the current crop of mobile OSs out there, it is by far the best designed.
From the underlying infrastructure used by the development team (one of the few teams at Microsoft I've ever been on that really believes every daily build should be stable and reliable, and has the test infrastructure to ensure it[0]) to the lovely UI to the outstanding performance requirements the team places on themselves.
Back when I was on the WP team, a list of user frustration levels with wait times was widely disseminated. It was something like " 50ms unnoticeable to user, 100ms+, somewhat noticeable pause or skip, 250ms, interface begins to feel slow, 500ms+, user satisfaction begins to drop, 5s+, users become overly irritated" with a lot more detail and gradations of course.
The team's internal requirements was that all UI elements in the OS respond in less than 1 second, and even then, you'd better have a damn good excuse as to why what you were doing took a whole second!
The UI flies. Animations are smooth and beautiful. Anything that does not please or delight the user does not get into the code base.
The bar in Windows Phone is not "do we have this feature", the bar is "does this feature make the user happy?"
All of this is of course not spoken as an MS employee. I'm just a lowly dev, albeit one now in charge of a UI dev team, and I can tell you that our product will sure as hell meet the same bar of smooth beautiful performance that Windows Phone does. It is damn well going to be a matter of pride if nothing else, and the entire management chain here is behind me on that!
[0] The Windows Phone division has over 4000 people in it, although I am not sure how many of them are devs. Let's say 500 or so devs total (likely an underestimate!) checking in code to what is a huge code base. Now imagine every single day, you can take the code that is committed and, without worry, put it on your phone and expect it to work. Daily's aren't always 100% stable, but they are dog-foodable and usable. One thing I miss about working there is coming in every morning and flashing the latest code to my phone and seeing the incremental progress that the team made on a daily basis.
Of course this ignores that many teams work off of branches which are then tested and integrated. The overall engineering effort to keep that platform moving is huge.
If only there were a third mobile OS for you to try, one that's actually well-designed, one that even many Google employees use ...