I'm running a Nvidia Geforce GTS450 and the above drivers cause majority of the games I have to run either poorly and/or get artifacts.. I just wanted to give folks a heads up in case you were considering trying the beta drivers out. I'm thinking I might be in the minority with this driverset since I have fairly old hardware. I'm back to using WHQL 296.10 as those run perfectly.
I've got a GTS450 too. The 301.24 beta drivers didn't give me much issues. Although, I did notice a occasional black tears while playing a few games. The frame rates were ok though. I currently use the 267.85. It's been the most stable for me.