I posted several months ago about how I was going to give DC Universe Online a go since it was free to play on the Sony PlayStation Network. I am not a huge MMO player. I fiddled with Dark Ages of Camelot and I have played (and now own) my share of MUDs and I did log about four years on and off on World of Warcraft. I have briefly tried a couple of the other free MMO's in the past, and they just never 'stuck' with me the way WoW did.
It is absolutely worth going back to the underground for these updated titles