It might be no surprise for you, that - especially after I've unlocked my 1000 check-ins badge today - I'm a big Foursquare friend and user. Following earlier this week's great v2 4th & Mayor upgrade, today also Foursquare itself has relaunched it's Windows Phone 7 client and brought it to v2; which finally comes with a lot of improvements and enhancements. While the original Windows Phone 7 Foursquare client was somewhat basic and buggy, lacking a lot of features, v2 supports all the latest and greatest Foursquare features. First of all, it comes with a new design and looks more colorful now. However, finally it also shows Foursquare specials around, allows to explore and even also allows to upload photos to check-ins now.
All this isn't new for other platforms but so far it wasn't supported on Windows Phone and some of the features just became supported recently with the 4th & Mayor v2 upgrade - which is still a great Foursquare alternative.
Nevertheless, there's still no Live Tiles support which means users wont get any check-in or comments notifications pushed to the Windows Phone.
If you have the v1 Foursquare client already installed on your Windows Phone, you won't receive a notification that an update is available because v2 appears as a totally different client. Therefore users have to manually search and install it separately which means that two Foursquare clients will be installed on the device - v1 and v2.
Cheers ~ Arne