Approximating 350 MHash per GPU works out about 15,000 GPU's for the network's ~5 THash/s ... so actually an overstatement.
350 MHash per GPU average? Perhaps you could re-calibrate including the nvidia vs Ati market share ^^
your figure is not so much off anyway, still I think it's quite a big number... when you say "nothing compared to everyday stuff", well, I think there's a bit more than what you think... it's a geeky thing but it's still impressive!