tested on unity 4.6.20(beta), unity 4.5(latest version)
unity is fine so far. but monodevelop is not working.
when i click script file on unity or double click monodevelop app in application folder,
Monovelop icon disappear after bouncing on dock for few sec.
i can’t open it.
Its something with permissions.
Right click on MonoDevelop in the Finder and click 'Show Package Contents", right click on the ‘Contents’ folder and click “Get Info” down at the bottom of the info window, for ‘Everyone’ change the ‘Sharing and Permissions’ from ‘read only’ to ‘read and write’. Finally click the wheel icon at the very bottom and click ‘Apply to enclosed Items’.
I had the same problem. 