I just switched my desktop (the one with the GTX970 G1 Gaming) from windows to linux and got a very nice surprise: on windows, when mining, the mouse is lagging and the machine is pretty much unusable. On linux, no such thing! The machine is happily mining Quark at 17MH while I watch a 1080p video on Youtube.
I usually use the internal gpu of the motherboard to do the display in windows, and the cards 100% for mining.