Free MMOs don't go very far at all...Trust me! I've played Tantra, Maplestory, Cabal Online, and Trickster Online. All of these MMOs are rather reptitive and get boring after a given amount of time. However, if you WERE to try one of these.... Cabal Online would win I think.
Tantra is based in the phillipines which makes it difficult to ask for help (Though it's a pretty good game).
Maplestory requires endless hours of grinding and pressing a few keys over and over, however the large community is kind of fun to laugh at (Mostly 13 year olds who want to marry in game and spend loads of cash for special items).
Cabal Online is actually really well-rounded. I played it for quite a while and it wasn't as reptitive as a lot of games. The concepts and details of the game make it fun to play for a while. However don't download from cabal.com because that is the European version which North Americans can't access. If you were to get this game, download it from ogplanet.com
Trickster Online was a very brief game that I explored. I was on of the first to start playing it and was near the top in levels, but after hitting level 40 it got pretty boring.
My personal opinion: If you really want to play a free MMORPG, find someone you know who is playing one and join them, it's less of a headache learning everything. On top of that you have someone to help you and give you items. JUST REMEMBER THAT MMO'S ARE A HUGE TIME KILLER AND RESULT IN YOU EVENTUALLY QUITING IT, PLAY CS:S AND BE HAPPY YOU HAVE A QUALITY FIRST PERSON SHOOTER TO PLAY!
That is all.