Tharsis Gate has the best skill system I've seen out of any game I've played. A fun training system where you train from other players, rather than going to an NPC or training room.
The guilds are all fun and have noticeable differences (As opposed to many other muds where the guilds are just the same with different command names)
Stats are simple, rearrange at the beginning and max them later. Thank god, because raising stats is boring.
I love the atmosphere of TG... newbies get treated like crap for the most part but if you can make it through the first few abuses without flipping out on anyone you'll quickly earn the respect of the players. Everyone jokes around with eachother and most of the players are very social (as are a few of the wizards(GMs)).
Hunting is basic hack-and-slash with timed guild commands, makes for fun combat when you use commands in the fight.
There is an open call for Builders which is basicaly a developer without any more power other than to make an area, if you make a good area or two and wish to become a Wizard you can as I understand it as well.
Role Playing is non-existent. But encouraged
I've played Tharsis Gate for 3 years now... it's one of those MUDs you love to hate (aren't they all?). Tharsis is in the middle of some big changes nowadays and from what I can see they're all for the better. It's not for everyone, but come check it out you're missing out on one of the most unique mudding atmospheres out there if you don't.