To my opinion it's not so profitable as is used to be but therr are still opportunities for arbitrage trading. Although it's not always easy to spot and catch such chances and you really should be very dedicated to such type of trading to achieve some results. And you have to count of great deal of risk too.
i found that the arbitrage trading tend to be speculative even at the end it seems like a lucky based trading technique. you have seen the chcance is there, the gap is there pretty clear for a while and you decide to start arbitrage but guess nobody know that when you successfully moved the coin, the price move down significantly unexpectedly.
that kind experience happened a lot of times.
at that moment you will think that at the end it alwasys about the lucky factor using this technique to trade.