Problem is a strategy of sitting back and waiting for like QQ+/AK and pushing all-in will probably beat the play money games and is probably the best strategy. It's not going to work in real poker though.
It does if you play the short stack strategy. Many sites won't let you buy-in at microlevels for only 20BB, though. Learning to play cash with a max buy-in can still be pretty expensive.
The main thing I learned playing with play money is to be patient. Not necessarily going all-in when I get a great hand, but waiting for the crazies to get knocked out, (or helping knock them out). That's a good thing for real poker, too, although I will have to admit maybe I'm too patient and need to loosen up some. Toward the end of a play money tournament, people play pretty normal. I think it's because although they have no money invested, they have time invested. It still sucks to lose after you've put a lot of time into something. The neat thing is you can play correctly for the situation and not have to worry about losing money, which might make you play too timidly.
I've always felt that the best competitions don't have money riding on them; just playing for pride is a great motivator. The Olympics epitomizes that. I even bet that for some well-to-do poker players, they'd rather win a
wsop bracelet than the money. Money is fleeting, you win it, you lose it. But you'll always be a bracelet winner and that's what people look at when they compare the best players against each other.