Quantitative Trading, Any real experience?

I just finished reading a book by Ernie Chan, Quantitative Trading: How to Build Your Own Algorithmic Trading Business, just wonder any one had real experience to use Quantitative approach to trade stock? Consider the fact that investment bank, hedge funds spend hundreds million dollars each year to develop the stock trading strategy, optimize the portfolio, price the derivatives and hedge based on quantitative approach, there must be some interesting quantitative analysis. Otherwise, there is no quants in this world.

Although I agreed that the stock price on average are very closed to random walking, however, it does not mean that under certain special conditions, they cannot exhibit some degree of mean reversion or trending behavior. If only we could capture the moment, we could beat the market.