same here, i'm struggling right now with 263.14 as 265.90 don't work :(
Got BSOD with this
I've got the same performance with my GTX 460 FTW EE on my E8600 and on my i7 875K, but SLI require more CPU cycles so don't really know :)
Using 260.99 atm ! Memory drop down from 2000Mhz to 1000Mhz on desktop.
Got a Samsung 2233RZ too, 120hz on desktop, and 2D clocks for memory !