This is pretty simple and has probably been mentioned already. But on an SLI system, you may find that your mouse is disappearing on one half of the screen, even if you use hardware mouse pointer. In the NVIDIA 3d settings, I had my sli rendering mode set to autoselect, and it worked for the first day I had the game and then the pointer started disappearing.

To fix this, set the sli rendering mode to single gpu rendering mode. You'll need to have it show advanced options to see this setting. Some of the other rendering modes may also work, but I haven't tested them. You could also disable sli mode entirely, but that can get to be a pain if you play more than one game. Hope this is useful to someone.