Overall i'd say Avatar is one of the friendliest MUD communities i've been to. Most people will help you out with questions and such. It's very easy to learn the ropes in this kind of environment. More MUDs should have this kind of atmosphere
I don't know of any MUD that's RP(though some may advertise that to lure players). If you want to RP look for a good MUSH(This was just a comment about the previous reviewer).
There are alot of things to explore and I guess they are working on new areas. You'll need to group with people at higher levels so those looking mainly for solo adventures will probably want to seek a different type of MUD.
My only negative about the MUD is that it lags at times(a little more than i'm used to with MUDs). Maybe someone on the staff can say what the deal is with that.