Not long ago I mentioned I was a bit of an MMO whore, but in recent times I haven't been playing much. This means I have never really been around for the whole 'free to play' MMO games in recent times. While the business model seems to work, I don't particularly like the gameplay traps that most of the games seem to fall into.
A lot of the F2P games follow a very 'eastern' progression model (i.e. grinding), which I personally detest, but F2P extends on this by either emphasising the grind unless you pay to access areas that give better rewards or by providing the rewards themselves at a cost. Even western games that are now F2P have a similar trap, with D&D online and Champions Online allowing you to pay for the better quests.
To be honest I think I prefer the 'unlimited trial' model of WoW and W:AR, where you can pretty much do everything any other character can up until a certain level, though not everyone will agree.
League of Legends is a F2P game that I am really enjoying though, perhaps because it is not an MMO and has no real grind. You can pay for new characters, skins, and minor abilities, or you can use earned points to purchase these items. A real bonus to LoL is the continual cycling of the character roster however, so every now and then you will get a new list of characters to choose from (plus any you purchase) which means you are not stuck with crappy stock characters even if you play rarely or don't want to pay. Since most of the 'power up' abilites can only be bought with the 'earned' points, and not cash, you never really feel cheated by not paying either.
But all in all, I have yet to find a F2P MMO that even comes close to interesting me the way subscription ones do, and it seems the majority of the subscription games that have turned F2P are the grind-y ones that I was never really interested in anyway.
Perhaps i am just getting old and MMO-hating rather than F2P hating, we'll see what ToR does for me :)