Just thought id add my experience with the asus P5B-VM as ive just finished building the system.
As mentioned elsewhere in the thread overclocking is pretty poor, im far from an experienced clocker but i still like to have a go.
Bad news is anything above a fsb of 274 and it wont boot. One problem im aware of that doesnt help is the Memory i have is rated at 2.1v and of coarse this motherboard only goes up to 1.95. Ive still got a few things to try and i shall report back if i can get it clocked any further.
The total system spec is:
Asus P5B-VM
Intel core 2 duo E6600
2GB GSKILL 6400 HZ
EVGA 7900GT 256mb
Overall though i am very very happy with the system. Its far better than my AMD64 3200 clawhammer/ FX5900gt system. I can run games such as far cry and quake 4 at maximum graphics settings and it runs as smooth as silk.
I do feel the lack of overclocking is a waste of my cooling system though - Swiftech storm CPU block, Maze4 GPU block, D5 variable pump, thermochill PA120.2 and 2 x Scythe S-FLEX 1600RPM fans all tied together with 7/16th tubing.