From my experience, the problems begin once you get to Charing Cross. The game crashes after some time, usually when you re-enter a station, sometimes with a "memory leak" message. Weapons become invisible, huge loading times, bugged quests,tje occasional freezing, lots of issues. There is one buggy quest which keeps you from playing on (I have heard in the Hellgate forums, I havenīt advanced that far yet... mainly because I had to play each major level 3-4 times
). It does seem to be an issue of hardware, many people in the forums complain about these things, even those with powerful machines. My own computer easily fulfils the requirements. This seems more due to sloppy programming and/or a rushed market entry.
The game itself is quite fun, like Diablo in 3D, but with even more feautures to personalize your weapons. The storyline is kinda thin, though.