I've been playing Realms of Despair for five years now, and I've been an imm there for two years. I'm not the kind of person who likes MUD's at all, I've tried others, but I've always found a home at Realms of Despair and would (and have) recommend it to anyone.
Realms of Despair caters for every kind of player. We have an active player-killing community (totally optional), a very active roleplaying community (again, totally optional) and a massive community of players who just want to explore the hundreds of areas and tens of thousands of rooms, and kill the thousands of mobiles that Realms of Despair has.
Newbie-friendly? Definately. Realms of Despair has a player-operated council that is DEVOTED to helping out new players. Got a question? We have channels strictly designed to ask for help and offer answers to anyone who asks.
Quests are run often, there are many Immortals who spend all their time writing new and exciting quests for all players to enjoy. Quests are rewarded with "Glory" which can be accumulated and exchanged for enhancements to your character or items, to make your sword the best in the game!
There are dozens more fun things that Realms of Despair offers. Active "Chat" if you want to just relax from having fun, our own magazine called the "Cry of Despair" which is published in-game monthly, dozens of clans/guilds/orders for you to join, and too much more that you'll just grow disinterested from reading such a long review.
Try out Realms of Despair, I have no doubt that you'll enjoy it as much as I have these past five years!