Yes, Mountain Lion is out. Well, I may wait a while on this one. So far I haven't heard about any problems except with Python modules.
When upgrading the system to Mtn Lion, the installer removes previously-installed Python modules. All you need to do then is run the framework and python module installers to restore my Python modules. Also, since there is no Python 2.8 for Apple to upgrade to, the default Python is still 2.7, so this makes it simpler for me to make my packages cross-system version compatible.