Well, I've just finished playing the Hellgate: London demo, and I'm way too much dissapointed with it :(
Coming from the makers of Diablo and Diablo II I was expecting something as addictive as those games, but with state-of-the-art graphics and lots of new things to do. Instead, what you get is a post-apocalyptic futuristic 3D diablo 2 clone :/
The graphics aren't bad, but not too great, and animations don't feel natural as in other games (both for enemies and sword fighters, I haven't tried marksman class).
Sound is normal to bad (nothing special and really poor voice acting).
Gameplay is a pure hack'n slash, not similar but almost exactly the same as Diablo, but in 3D. You even have the equivalent of the horadric cube to mix items...
Overall, I was expecting a ton more. If this were a one-pay game would be ok (and I maybe would even buy it), but having a subscription fee is just a waste of money.