I installed the "new" OS X - Mountain Lion - 10.8. This is the more un-hyped version of the operating system. The only usable features I found were Notes and Notifications sync with my iPhone, so far they work good enough.
Speech recognition integration is good. Recognition actually happens on an apple server which sucks especially with no internet connection.
Unsigned pkg files are harder to to install. An option has to be changed.
icloud.com is very neat - Mail, Contacts, Calendar, Find My iPhone, iWork.
People say there are battery issues. I haven't tested.