I compared them to my 7506 (burnt in for a couple months now) and the bass is not developed yet (or kinda boomy). It does not sound shrill yet, but maybe because I am already used to the 7506's sound. I just remember that once the bass cleared up, the brightness came through but I guess that won't be a problem for me.
Also, physically, the two are identical except the V6's cord is slightly (barely) thinner and the coil (width) is also slightly smaller than the cord on the 7506's. It's such a small difference that you really have to hold them up close and look for it to see it. The plug on the V6 is completely copper (?) and silver in color up to where the cord joins it while that part is black on the 7506's except for the gold plug.
The 7506's cost me over $100 with shipping so this purchase compensated for that high price nicely (works out to about $70 per set). Both are in great condition, but I may give one away as a present. Thank you Head-Fi, for I owe both purchasing impulses to this board.
Edit: Actually, the burn in process is almost done after just about 3 hours. So I guess they were burnt-in pretty well previously.