It's a great game, but I've quit and restarted it so many times over the years it's gotten a bit stale now. That and it doesn't have a very active community.
I don't know whether there is an active community out there for a niche game like that, but if there is I sure would love to hear your suggestions.
EDIT: Hell, it doesn't have to be too similar to it. Browser based is a place, but I'm just looking for something unique, addictive and with a strong (tight-knit) community. I'm open to suggestions of what you personally feel is a very good game.