f2p? Nah, I don't like f2p games. I prefer the typical American style billing system where you pay a flat fee by the month or in blocks of 3+ months at a discount.
A few points on that.
Griefing is a problem, yes I agree.
Other thing is it throws off player balance, I mean there really are no "free" games (other than a few crummy games in perpetual beta) and what they do is sell in-game content to raise money to support the servers and staff. But what this does, if other than a "solo" type game... which makes no sense for an mmog, is that when party groups form, often some players will be nerfed because they don't have the uber equipment that the other players bought. So if you think about it, that means those players are lagging the party and bringing down those that pay for that equipment, taking away from their game experience.
Another point, most of the f2p games are isometric. Isometric takes more bandwidth to operate than a classic MUD, but far less than a full 3D environment, and bandwidth costs. Many that do f2p in a 3D environment rely heavily on instancing, and I dislike instancing for the most part. I much prefer the classic style mmog were it has little or no instancing and players are actually emerged in a perpetual game world.
Another thing, not really so much regarding f2p, I don't like expansions you pay for, but just added zone/world content to all accounts so everyone has access to everything. I'm really big on player balance (non-pvp), so having players unable to get to content I feel throws that all off. Most AAA titles don't do that since they want to publish a expansion box so to have it on a store shelf, but it messes up the game world imo. There are some AAA's that have been doing it the way I just mentioned though, like CoH to name one, I mean as far as just publishing new content w/o fees, though they fall short with so much instancing as not being the perfect model for an mmog of imo.