While Foursquare's Windows Phone 7 client was available right with the launch of Windows Phone 7 last year, Foursquare hasn't updated its app in any way to either fix some of the nasty bugs (for instance umlauts or other special characters are still not supported which means users can't check-in to locations which contains it) or support some of the latest Foursquare features (including photo uploads from locations or commenting on check-ins). However, thankfully there are some smart developers out there and Jeff Wilcox, a Senior Software Development Engineer at Microsoft, is currently working on a new feature-rich Foursquare client for Windows Phone 7 which is called 4th & Mayor.
Strictly following the Microsoft Windows Phone 7 Metro UI guidelines, 4th & Mayor features a beautiful, clean design and layout. It support all the basic Foursquare features like searching four locations, seeing friends check-ins as well as checking-in to a location but it also supports photos and comments. It's possible to comment on check-ins as well as adding photos to places and tips. Furthermore it supports recommendations and leaderboard features. And yes, 4th & Mayor supports international, non-ASCII characters as well!
And there are even additional features in the pipeline for future updates which includes Foursquare's specials support (including all the new special types and location of nearby specials when viewing places), enhanced notifications about friend requests, specials nearby, etc., additional performance and usability fixes as well as the ability to add new Foursquare locations.
Right now, 4th & Mayor is available as a free public Beta download but requires an either developer or ChevronWP7 unlocked devices. However, the website mentions that the app is now pending for Marketplace approval and should therefore be publically available soon.
UPDATE: 4th & Mayor is now publically available as a free download from the Windows Phone Marketplace.
Cheers ~ Arne