If we'll be back maybe several years ago or maybe even a decade, I think that it's profitable. But seeing that the exchanges have competitive prices for the pairs, it's hard to be profitable through arbitrage. It is profitable if there's a good margin you'll be getting with your trades considering the fees included and the time you're spending on it. Because the market is so highly volatile, and the time(speed) is important if you'd found the perfect pair and the exchanges where you'll do it but most likely, you'll have difficulty in finding one. That is because prices can change almost an instant and instead of profiting from that, you might see the risk that it has got by losing. And if you find few exchanges to do it, don't be surprised that you might not be able to repeat it on the same ones you did it.
This is so hype before because there are many people made good profits for doing this. But now I think situation became so different. Since market is so challenging and now everything moves fast.
Even if they spot a huge gap from different exchange, there's tendency that they might going to lose their trades especially if there's a delay happen of sudden price shifts.
But its still possible to earn from it nowadays, but its so rare for people to earn with it consistently. Because for sure that they cannot continuously repeat those situations. Well maybe if they are lucky they could spot some good opportunities on each market they visit.