I gotta say I much prefer monthly subscription MMOs over one time fee ones. The quality of gameplay is exceptionally better. People are nicer and chances that you will be scammed are much less. The monthly fee goes to pay for consistent updates, not only for bugs, but constantly and significantly expanding the options for what you can do in the game.
Because a players account is tied to a credit card they are no longer just another anonymous person on the internet. It cuts out that factor of all the people who are going to be jerks just because they can. I quit playing counter-strike for quite a time because of the horrible game play atmosphere. It really sucks to be trying to play a game and one, two or a few people are going on about how "gays, jews, fags and niggers need to die" and how much they love Hitler. Not to mention persistent cheating.
If people do actually do such offensive things as the above the constantly on-line GMs are not far away, and the person can be held accountable. You can even get your stuff back if your account is hacked.
Having moved from one time fee / free MMOs to subscription based ones I would never go back.