Heck, it took FFXI a good 6-9 months to even start catching its stride and getting all of these scalability/code bug issues worked out. Once they did though, it was pretty stable. If you can't remain patient through the debugging phase of a new game, you're better off waiting until the word on the street is that things are solid before jumping in. It's generally expected that things will be this way for a while.
It was stable until Windows 7, at which point POL randomly started crashing for no reason at all at least once a day.
That's a client issue, not a server issue, but it still annoys me greatly.