I installed OSX Mavericks on my Mac Pro (2012, 32Gb, 6-core 3.46GHz, ATI 5770) yesterday and I am not very happy with the experience so far. I'm on the latest developer preview DP3. Stability seems to be good and most programs are working but the performance has taken a dive compared to Mountain Lion 10.8.4 on my system. My Geekbench result with Mountain Lion is 16200. With a clean install of Mavericks (from a thumb drive) with no third party applications installed I get 15600. I thought it might be a compatibility problem with Geekbench so I tried opening a few of my projects in software such as FCPX and Logic Pro to test real-world performance. I found the difference to be very noticeable, both programs perform worse than in Mountain Lion in terms of cpu performance. Anyone have an idea what is causing this? Is Mavericks optimized for newer technology than the 2012 Mac Pro (which is essentially a 2010). Has anyone else experienced the same thing?