Hopefully it will fix these bugs (some of which I sent to Bug Reporter):
-Memory Leaks in certain Nvidia GPU's
-Green button zooming in the finder "Icons" view not correctly resizing
-Slow shutdown caused by "appleeventsd" hanging for 20 seconds before being terminated.
-battery life (has gradually improved since 10.8.0)
-User Interface performance. Especially with Mission Control and desktop switching. (Lion improved over its iterations, hopefully Mountain Lion does the same)
-Not permanently saving custom folders in the "Desktop & Screensaver" section in System Preferences
-QuicklookSatellite process eating %150+ CPU time when trying to generate thumbnails for certain media files. Related to sandboxing. Workaround is here:
https://forums.macrumors.com/threads/1463364/
-Re-enable the ability to use a laptop with the internal display de-activated when connected to a monitor. Currently one needs to place a magnet in a certain spot to trick the computer into thinking the lid is closed.
This command "sudo nvram boot-args="iog=0x0" no longer works in 10.8.2 .
Edit
-Launch Services constantly creating duplicate entries in "Open With" when working with multiple Mac OS partitions
-Spotlight privacy settings affecting other install partitions. This bug began in 10.7 for me.