Problem is that the buyprice of a coin is always higher than the sellprice if you don't create the orders yourself.
Though it may not charge Trading Fees for the exchange itself, you definitely "pay fees" through buying for a higher price and selling for a lower price.
Of course, the absence of Trading Fees for the exchange itself lowers the difference between final buy/sell price.
However, this difference is negligible, due to the huge differences between buy/sell price, unless you use exchanges & trading pairs with enormous volumes, but CobinHood isn't a a high-volume exchange: Its highest volume trading pair is ETH-BTC, with about 115k $$$, giving a difference between buy/sell orders of about 0.6% currently.
Compare that to higher-volume exchanges that charge fees, but have lower sell/buy price differences, making your potential profits much higher.
Therefore, it's stupid just to look at the exchange fees.
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As some others have already noticed, the exchange does charge some relatively high withdrawal fees. Thus, it's only worth it, if you have a reasonable amount of cryptos to trade with.
However, due to CobinHood's low volume, you wouldn't be able to buy a lot without immediately driving up the price like crazy on the exchange. Thus, again, we'd prefer a high-volume exchange with lower withdrawal fees & lower buy/sell differences, than one without exchange fees.
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Though I must say: Try it if you want... Given the volatility of Cryptos, these relatively small variations won't make the difference: The rollercoaster rides of the cryptos will.
Hm...you made some very good points. Will take them into consideration.