They announced a while back that they would be moving away from 'cats' for OS X and onto things about California. So Mavericks is their first in the new California naming scheme. I too downloaded and upgraded my Mac Pro last night, also took forever because everyone was hitting the servers hard for the update. A lot of the little changes are nice and of course it is great that it is now free.
I'm seriously considering upgrading to the new Mac Pro come december. My current Mac Pro is from early 2008. While still performing great, it has become noticeably slower and the new Mac Pro is shiny. I'm still on the fence about which way to go with the iPad. Now that the iPad mini has the retina display and basically the same guts as the iPad Air, they are making really hard to decide between the two. I think I'm going to have to look at both together to decide. So come February or March their will be another announcement for the new iPad Pro?