It's hard, I've tried it, and it does not work, most of the exchange will quickly respond to rising and declining bitcoin prices,
I think that there is still a significant price spread between some of the exchanges. For example, the exchange rates in BTC-e, on average will be $50 to $100 less than the rates in Bitstamp and Coinbase. But you can profit out of it only if the prices remain stable. Also, you need to check the fee for fiat deposit and BTC withdrawal in these exchanges.