I have it, it's quite good. The latency issues were atrocious when it was first released, but all is well again.
I started the series with Tekken 3 for Playstation, then played Tekken Tag extensively in the arcades (didn't like it on PS2 though, it felt "off" to me) and pretty much ignored Tekken 4 (it sucked) but really enjoyed Tekken 5 though the lack of online play meant I had no one to play with.
Enter Tekken 6. It's great, I'm really into it but have been playing too much Modern Warfare 2 lately to stay sharp. I'd say it's the best entry in the Tekken series by far, they've reworked so many of the old animations and added awesome new stuff. Tons of new characters too. My only gripe is some of the "bounce" juggles, they seemingly last forever but that's not news to anyone familiar with the series in general. I haven't learned the game well enough to know how difficult those endless juggles are to pull off so maybe it's balanced by degree of difficulty.
Anyway, yeah... the game is seriously good. Kind of annoying how expensive they made the custom clothing items though...