The release notes say that:

The Release 275 beta driver v275.27 can cause significant performance drop in The Witcher 2. This issue has been resolved in v275.33 drivers. Please read this FAQ for more information on this issue.
•Increases performance for GeForce 400 Series and 500 Series GPUs in several PC games vs. v270.61 WHQL drivers. The following are some examples of improvements measured on Windows 7. Results will vary depending on your GPU and system configuration:
GeForce GTX 580:
◦Up to 4% in Crysis 2
◦Up to 5% in Civilization V with SLI
◦Up to 9% in Portal 2
◦Up to 13% in Bulletstorm with Antialiasing enabled
◦Up to 15% in Batman: Arkham Asylum with PhysX High
GeForce GTX 560:
◦Up to 6% in Crysis 2
◦Up to 8% in Portal 2
◦Up to 14% in Batman: Arkham Asylum with PhysX High
◦Up to 15% in Bulletstorm with Antialiasing enabled
•Increases performance by up to 12% for dual-core CPUs in CPU-limited cases.

Here are my 3Dmark06 numbers

3DMark06 results

Official 270.xx driver 13950
Beta 275.27 driver 14057
Official 275.33 driver 13693

The latest oficial drivers give me less numbers in 3Dmark however its performance in Bad Company 2 seems smoother and probably gives me few more FPS.