I lately had my MacBook Pro Retina with Yosemite (OS X 10.10) freezing quite often, the only thing that still was working was the mouse moving around all the rest was frozen.
In the console application there where several "GPU Reset" entries. I then googled this and found out I am not the only one. There is a bug in Yosemite or the driver for the graphic card that apple has to fix, the question is when will they do it. Here is a discussion thread on the apple website: https://discussions.apple.com/thread/6602046?start=0&tstart=0
The title says mid 2012 models but it's not only that one having problems.

It seems the freeze accures when your MacBook Pro switches from the integrated to discrete graphic card.

A workaround is to set your graphic card to discrete and disable automatic switching. You find the setting in "system preferences --> energy saver".
This did not help all, including me. I then downloaded this app here: https://gfx.io/ where you can switch it to automatic / integrated or discrete.

Hope this helps others.

Best
Michel