Single player mostly, the way this game works, all the instances/dungeons or whatever makes it so you're pretty much playing alone or with a party. You will never get some random intrusion from other players or such.
I haven't touched Hellgate London in ages though, not since Stonehenge came out. I wonder if you get all the nice features for single player or its all completely made for multiplayer.
Some things have been moved over, but not much. No content additions, quite a few of the bugs remain (despite the fact that SP patch 1.2 came out), and other irritations remain as well.
As for the MP aspect, anyone who tells you it's worth paying for doesn't know what they're talking about. So many of the original benefits of being a paying member were passed over to non-paying members that it isn't funny. And the gameplay still isn't much better.....
All times are (GMT -08:00) Pacific Time (US & Canada). Current time is 3:24:23 PM