I've been playing AR for about 2 years now and I've come to find it to be an incredible place to play. I came to AR with about 6 years of previous MUD experience in some of the more popular internet games of the time. I have to say, AR was a complete change for me and my style of MUDding. The PK is aggressive, the RP is enforced and things are constantly changing and getting better.
There are some cons, I can't lie - but I will say I've never played a MUD where the staff take so much care in making the game perfect and fair for everyone. They listen to what the players have to say, and often ask for opinions on new things, and institute them in the game within the week. The playerbase is quite nice, and growing since "The purge" a couple of years ago.
I'll say if you're looking for a great MUD. This is the one for you.