My experiences are the same as Pyros. Houses were a great idea, but the implementation was so bad with the abnormals it really made the game a pain.Most of the memories I have about housing in UO involved griefing, stacking those items(books I think? boxes maybe) that actually had volume to make a stair to walk into the open courtyard of blacksmith houses and looting them since most people didn't lock the inner doors, walking through the stairs of a small house to get through the floor, telling the guild leader of an enemy guild that we wanted to discuss a ceasefire then stealthing and snooping in his bags to steal the key to the house while he was talking to my GM and opening a portal straight to our guild house and emptying their guild house while they were still talking, stealing runes to blocked keeps entrances(could use small houses all around the entrance to create an artificial wall) then camping them there using a bunch of people on the steps to prevent them from being able to shove their way through into their houses before they died, raiding the player run cities during their roleplay events, and so on and so forth.
The best housing system is the one from SWG.