According to Notch's blog, the Minecraft Beta 1.5 Update released on April 19, 2011 contains some pretty cool new features to this already amazing sandbox game. The new game enhancements include:
Weather including Rain, Snow, and Thunder Statistics Achievements Detector Rail Booster Rail Performance Enhancements Notch says that currently the statistics and achievements are stored locally, so I would hold off on uninstalling your game until they implement a server-side storage solution. He also says that more stats and achievements will be added over time, so this could be a very cool update.
I haven't actually been in-game that much recently, so these new enhancements should be a pretty cool site to see the next time I play.
Happy Mining and Crafting :)