Hellgate Rocks. It is wicked fun that grows on you very quickly.
Example of computer needed to run this game and get the full graphic benefit:
I have 3 PC's in my house with Vista. One of the has a C2duo E6300 OC's to 2.4ghz, 2g RAM and a 8800GTS 320. When we turn on dx10, it is almost unplayable, but in direct X 9 with modest settings, it works well and is very playable. But the graphics to look a little dated.
My PC on the other hand, has a E6850 @ 3.8ghz with 4G RAM (64bit vista), 2x8800GTX, and I can play @ 1600x1200 with everything all the way turned up except for AA, which I turn on Medium, and it is as smooth as glass!! (turn off vsync!!) And it is absolutely gorgeous!! Most likely I will use this game to show off the graphic power of my PC it looks so good.
The only thing I can see as dated is the way your character runs. It is a little stiff. And, the voice acting is not the best, but it is not the worst. I feel these quirks are made up for with the great gameplay.
As far as gameplay goes, it is not like anything else, but very easy to play, learn, and get addicted to. I can't wait to try more of the clasees. I think this may be one of those games that people will hate or love, but not really much for middle ground.
I say if you have a bangin' system, it is a must have, but for those with lower end rigs, you may want to wait until a price drop and an upgrade.
Also, I have not tried the multiplayer, but that is not why I bought this game. Still, I plan on trying it soon.