I'm stuck with T-Mobile for another year, so I picked up a Nokia Lumia 710 to replace my crappy Samsung Vibrant stuck on Android 2.2. The first and biggest thing I will say is, there's no "useful" apps on WP7.5 like there are on Android (or iOS). However, once I got past that for the first week or two, I've actually found the thing to be better in a few ways:
1) The OS is constantly responsive, no stuttering like I experience with Android, comparing even to a Tegra 2 tablet running ICS / 4.0.
2.) GPS locks on instantly - a huge issue with the Vibrant, and apparently still an issue with select Samsung Galaxy devices)
3.) Battery life is awesome, can easily go over 36 hours of mild to medium usage, again compared to my Vibrant that lasts about only 18 hours.
4.) On the fly locational searches work well - It passed the "girlfriend" test in finding the phone number to the corner pizza shop. Android would pull up a browser with a whole lot of links to click; Windows Phone brought up something similar to a contact list (even though they were not in my contacts), displaying addresses and phone numbers. Definitely a much cleaner solution when you're looking for contact info.
Overall, I'm impressed with it, but the platform really needs more developers to port their apps over from Android or iOS.