Update Wednesday has begun! We're starting off with a pretty small bump for Google Play Games, taking it from v2.1 to v2.2. There aren't any big new features, but a few things have been polished up.
Like so many other Google apps, the first-run experience has been updated with a short introduction to explain what the app does and the value users can expect to get from it. Of course, this generally won't show up if Games has been in active use already.