I've played every free to play mmorpg out there, you name it I've played it. However a few weeks ago I tried a new one called Runes of magic and I was blown away. It actually felt like I was playing a pay 2 play mmorpg that was a clone of WOW that I actually ended up playing longer. They update the game every two weeks, evening out classes and adding new things to the game. This is the best free mmorpg currently out, it even beats some pay 2 play ones.
Only downfall is that it's a 4GB download :(.
A quick look at the game.