1. Mountain Lion's new security, Gatekeeper, does not recognise UoC as being from an identified developer so will not let it run by default. Need to CTRL-click the app to launch it and confirm that you do want to allow it. (Or change your Security & Privacy settings to allow any software to run - maybe not advisable!)
2. UoC requires X11 to be installed - on Mountain Lion this requires you to download and install XQuartz version 2.7.2 from xquartz.macosforge.org
Apart from those 2 hiccups appears to run nicely
