"The Apple TV support page had not been updated at press time with fixes and improvements in software version 2.3.1. Readers are invited to let us know in comments what amazements, if any, come with the update."
In fact, the only thing we do know is that third party add-ons and hacks have been wiped out for people who did the updates. That's to be expected, of course, and is nothing new from previous updates, but nonetheless if you're running Boxee or ATV or any of the other hacks, you may want to hold off on this one. Maybe eventually Apple will gift us with the knowledge of what this one fixes.