I've messed around a little bit with it, but I know some of my quant friends do it more seriously. There's definitely ways of making money of betfair, you even occasionally have arbitrage opportunities across the different markets on betfair.

I think the fundamentals are close enough that it's a useful place to learn. You're not going to be able to take a method that works on Betfair and apply it to a real market, but a lot of the statistical mining/predictions techniques you can use of betfair are exactly the same as those used in real markets.