The simplest way I can describe Rift is like World of Warcraft with a much lower population and less to do, with more character and class customization in a less cartoon-y world.
If you enjoyed WoW or very simila games, you should try Rift. If you became burnt out on MMOs or WoW-like games, this will not help you.
If you're still interested after reading the above, you should know that while there's nothing crucial that you have to pay real money for in this free-to-play game, the conveniences are expensive. You will immediately want to increase your character's bag slots from 3 to the maximum of ... 8 or so? That will cost real money of between $20-$40 for EACH character you create. Want to not grind your face off on the same repetitive fetch quests and kill X number of monsters quests? Be prepared to shell out $$$ for boosts, like any other "free"-to-play game.
I don't mean to trash this game, it's going to be fun for a lot of people and you can tell that the developers are actively interested in the long-term growth of the game with the new expansion out. If you dislike and/or are burnt out on MMOs or the "free"-to-play money schemes/systems, you should definitely pass on Rift though.