I have been a player at Midnight Sun since 1995. Although I've tried other MUDS, Midnight Sun has been the best. The players are very friendly - almost a family-like atmosphere. When tragedy strikes players in RL ("real life"), the MUD players come together and support them. I have not seen a "sense of community" like MS's at any other MUD.
Because of busy RL life, I've had to stop logging onto the MUD, sometimes months or years at a time, but everytime I come back... Well, it's like family. They always welcome back the old folks!
So, if you're looking for great play (medieval fantasy) and great friends, come join MS.