It worked (for the most part), but it's been abandoned now. The best way I can think of to describe why is to say that while the low hanging fruit exists, there's far too little juice in it for it to be worth the squeeze.
Others have explained that the problem they've encountered is counter-party risk in that some exchanges may not allow you to withdraw, or the prices may be skewed because they're charging absurd withdrawal fees.
None of this was a problem for me - I found the exchange APIs almost universally hold that information somewhere if you hunt around enough for it, so I was able to account for this when scoring opportunities.
My reasoning was that from a birds-eye view it looked like the price differences were allowing for trades that would have a 1-2% difference. I reasoned that if I were to withdraw directly to the wallet of another exchange I could have a turnaround time on some currencies of less than five minutes start to finish - even 0.1% every hour would be an incredible rate of return when extrapolated to a yearly ROI.
In reality, while currencies did (and do!) trade with that difference frequently between exchanges, the volumes are tiny. Despite having funds to spend, there weren't any big-money buyers at the destination exchange, and within a couple of dollars (literally a couple of dollars) the bids at the destination exchange were back below the price of the source exchange, and I'd be in the red on the transaction.
Add in the fees, and there was vanishingly little profit to be made while taking bet-the-farm risks that whoever runs the exchange isn't going to elope with your bitcoins.
It was a good learning experience, though - so I'm ultimately glad I took a run at it.