I have one in my brothers HP rig. I got to about 520mhz core with it, the GDDR2 mem sucks though, didn't wanna overclock hardly. I've also seen 650-700 mhz on air with these cards. I scored about 4500 on 3dmark05 with 3500+ CPU, 1GB DDR, and 7600GS(OC'd). This is worse performance than my 6800vanilla with GDDR1.
I Think the GT would have been a wiser investment, GDDR3 and look at the clockrates(1400 vs 800)
They have badass cores though, and I'm thinking of getting another one, and running SLI myself.