As the title says. What's your favourite smartphone OS. I'm also curious why.
Since I always like to play around with my phone by trying one or the other customised firmware and kernels is my personal favourite Android. Negative here are only the required rights of many free apps and the fact that Android market only accepts credit cards for payment.
I was also playing around with iOS which is imho also a very good OS. There are also a few good things imho, one is the possible sync via wlan. It really works great. However overall iOS is to "boxed" for my needs, even with the possible jailbreaks and resulting possible modifications.
I'm curious to see your votes, keep them coming.