That depends on what you are looking for. If you are looking for roleplaying - it's there, but it's so muddled in inter-player politics in many instances that it is disgusting. Admittedly, I have heard MUCH better things about the European servers - so you may have better luck there.

I played UO for about 8 years. I finally broke when I realized that the roleplayers I played with had lowered their standards so far... well, they went where I could not follow. I was assaulted verbally OOC, and a player broke so many courtesies, showed no respect, and used OOC information willfully... and the community in general accepted that behavior. 
I just stopped logging in one day. That was in September/October 2006.

UO, mechanically, is nothing particularly special either. Nothing is overly 'broken'. I do still have my account, but I think UO continues to exist on the playerbase that simply can't move on for whatever personal reasons, moreso than new players joining it.

The new -client- overhaul will be out soon, but months after that, there will be a new expansion, as has been EA's practice year-to-year.

It's lower requirements are a nice draw for those that don't have the super-computers needed for most MMOs coming out (or even out now).

I may be a little jaded at having seen all the changes over the years, too.