If anyone wants to work in high bit depth for colour correction (which you really should) then Black Magic has a free version of Davinci which is actually very good.
http://www.blackmagicdesign.com/products/davinciresolve
Click on download for Davinci lite and choose your OS etc. There are also tutorials once you get to the download page.
The mac version can be downloaded directly
http://software.blackmagicdesign.com/DaVinciResolve/Lite/DaVinci_Resolve_Lite_9.1.4_Mac.zip