A Customer Think survey recently published some data regarding customer satisfaction results based on smartphone operating system. The survey found that Windows Phone 7 ended up being the most satisfying operating system of the bunch, followed by Blackberry, then Apple's iOS, then Android, with Symbian rounding out 5th place. The number of users surveyed wasn't equal for each OS though, so you have to take that into account. Actually, only 1% of customer reviews were from Windows Phone users, which seems to indicate that the few that are using Windows Phone are very satisfied. Given Symbian's extremely low satisfaction scores, it would seem Nokia may have made a good choice in switching to Windows Phone.
It's also interesting to note that the features users felt most important in affecting satisfaction were reliability and usability. Price was second to last on the list of determining factors with music player functionality being last.
Source: Customer Think survey