Bumped up to version 188.8.131.52, the official client does have some changes to note. The obvious is that it now supports the fast-switching (multi tasking) to improve the UI; the addition of Twitter's own photo service to media sharing; there's also a counter on your API requests in the Settings/About screen that frequent tweeters will want to refer to.
Unfortunately it looks like this is nothing more than a maintenance release. There's no live tile support (even a notification on incoming replies or direct messages would be nice), no more integration with any of the sharing services, and it doesn't feel as "metro" as client for Facebook or Foursquare.
For DM and multiple account support, this is a deserving download. It's just a shame that nothing is being done to improve the experience and provide an alternative to the people hub.