I've done alot of MUDing over the last 5 years, and gone from place to place. I won't name names, but RoD stuck on me for the first time last February 2005, and has yet to let go.
The guild system is evenly divided, so that no one guild gets more power than another. Yet they've (the game immplementors) also left enough room for improvement. Each class has skills and/or spells that are unique to each, so that teamwork becomes more possible, and neccessary, to fullfill certain quests or runs. There's also new races up for review too, I hear :). For those of you who prefer to hunt the most dangerous of prey: each other... there's a dedicated crew of PKers who want your scalp on their belts too :>.
The Realms are HUGE! I've wandered all over, and STILL find areas to explore (ie: die in, heh :D). THAT'S the bigest draw for me, as well as the ease of learning the commands. If you have trouble as a newbie (a new player), most of the people are willing to give you some pointers, and some help in getting your feet wet, so to speak.
Ease in learning the commands, newbie-friendly environment, and an everchanging class and guild system..... not to mention the enormous job of bushwacking your way through thousands of rooms...... keeps Realms of Despair interesting, to put it mildly.
My name is Ardath, and I AM a Realms of Despair Addict :D.