I've only played hold 'em with real money online. I rarely play since I can get my fix playing with my friends at least once a week. I play with very little money, so it's not like I'm winning big or losing big. I basically just keep playing with the same money I deposited. It goes up a little and down a little, but it is pretty constant over time. I just prefer to play with real money when I play online because playing with fake money is such bullshit. Chip stacks are so important in poker, and in practically every single fake money tourney I play online at PartyPoker, someone has 3-4 times the amount of chips as every other player at the table after the first hand because all the morons go all-in with absolutely nothing. Playing online with fake money is hardly even poker because you can't bluff people off hands. If a player put 15 chips in for the big blind, even if he has 3 high he's still going to call a 700 chip raise because he's not really losing anything. The only pure online game is Yahoo Pinochle.
I prefer playing with friends or at a casino compared to online by leaps and bounds however. Even though I have no idea how to read other players, it is still more exciting when the person right next to you is putting you to the test compared to someone at another computer that is probably jerking off his dog at the same time he's playing.