Now it’s my turn!!
How do You made it???
I’ve got a GTX 675MX on my new iMac, i’ve installed devdriver_4.2.10 and cudatoolkit_4.2.9 but Blender 2.65a shows only CPU rendering in cycles!!!
Please help!
I’ve got it!!!
I’ve installed cuda driver 5 and it works!!!
http://developer.download.nvidia.com/compute/cuda/5_0/rel-update-1/installers/cuda_5.0.36_macos.pkg
Ok just to clear something up if this is what you guys are talking about, The cycles gpu option doesn’t automaticly show up. So what you have to do is go to File>User preferences>System>and in the lower left corner click cuda. Then your still not done you have to go close user prefs window>Render>device>gpu compute. Then you are done 
i was confused for a LOOONG time so I hope this clears somethings up.