A new Google Play Store v3.5.16 started rolling out to some Android users in the last 24 hours. This version replaces 3.5.15, which brought a whole host of new features last time around, and reportedly brings fixes to those having trouble seeing purchased apps or experiencing force closes.
Additionally, improvements in snappiness were reported, but it could just end up being the placebo effect. I haven't found any other obvious changes thus far. Still, if you haven't received the update yet, there's no reason to delay it whatsoever - you'll find our download mirrors below.
And a few earlier ones:
Download (change the extension to .apk if your browser downloads it as something else for some reason, like a .zip or .bin) and install as you would do it with any other apk - it will replace the existing Market or Play Store with the latest version 3.5.16.