I tried the nVidia driver -- and the latest Intel Processor Graphics 3000 driver at the same time -- with "interesting" results.
The green band I'd get when viewing Youtube videos in Firefox went away, which was nice. Also in remission was a weird glitch where my two docked monitors would suddenly disconnect, moving all the windows to the notebook itself. Still saw a brief video interruption, but the monitors would reconnect fast enough that the windows stay put and I didn't have to select extend and move things back myself.
However, I started getting corrupt renders out of Adobe Media Encoder (CS5.5) which is rather more work-critical. (AME uses the CUDA cores of the Quadro 2000 to speed rendering.)
I went back to the Lenovo driver and switched Firefox to always use the Intel GPU. Renders went back to normal and Youtube is fine.
As it happens, I just now installed the latest Intel driver only, leaving the nVidia driver alone. That monitor disconnect glitch was bothering me and I wanted to see what might happen. It shouldn't affect rendering, I hope... but a test may be inconclusive because I also just installed the CS6 version of the Adobe software. Still, I'll let you know what happens.
Oops... forgot to hit submit. The video rendered fine, and after a few hours (far from conclusive) all three monitors are still connected.
W520 (2820QM, Q2000M, FHD, mSATA SSD, dock)Previous: T61p (died 1m past warranty ), Dell 8600, iBook ("Dual USB"), Gateway Millennium, Macintosh G4 , PowerPC Mac clone, Mac Duo 210, iBook (clamshell), Quadra 630, Mac IIsi, C-128, C-64, Vic-20