The list of fixes applied by the Mac OS X 10.6.2 update is pretty vast. One of the more pressing issues that needed to be fixed was the infamous guest account data loss bug. This bug occurred for some users when logging into a Leopard-created guest account in Snow Leopard. The result of this was loss of all data within your regular account. This has now been fixed.
For the rest, the updates focusses on fixing issues with fonts, graphics, Mail.app, MobileMe, network file systems, printing and faxing, and Safari. Since I personally don't have a Mac capable of running Snow Leopard, I can't tell which fixes were more pressing than others.
It has also been confirmed that Mac OS X 10.6.2 no longer supports the Intel Atom processor, as had become pretty clear already from reports. This means that if you exercised your rights by installing Mac OS X Snow Leopard on an Atom-based machine (netbooks, mostly), you'll have to avoid the 10.6.2 update for now, or roll your own kernel from the open source base underlying Mac OS X.
"My sources tell me that everytime a netbook user installs 10.6.2 an Apple employee gets his wings." You have to admit, that's hilarous.
As always, you can install the update via Software Update, or you can download the full update straight from Apple. Report success or fail in the comments!