Re: glxgears score for Fx6600GT.
I think there's an issue with twinview. Running with a two monitor setup, I get 3000fps with an FX4400, but get 13000fps if I switch to single headed or cloned. Under windows I notice the same performance drop (completely unworkable with the nvidia demos (dawn, pirate ship, etc.) unless I toggle single-headed performance mode). I get something like 2fps in dual-headed-performance mode, and somewhere closer to 60fps in single-headed mode.
Interestingly, SPECViewperf results come out basically the same whether it's in full twin headed mode or single headed under linux, so it clearly doesn't affect everything to the same extent.