As you can see total DEX volume dropped by 78% since January. Overall volume dropped by 72% which is slightly less. I'm a bit surprised because in theory growing pressure from governments should force people to use decentralized exchanges.
Another surprise is Bancor Network - the only DEX which increased its volume.
Also, the volume looks more diversified now, because the two biggest exchanges (Bitshares and EtherDelta) lost their dominance.
Looks like traders are not yet convinced of the advantages of this model. As has been said many times, the biggest problem with decentralized exchanges is the lack of liquidity. I think this could be solved only by starting a DEX with built-in market-maker. So, a significant part of the ICO funds should be spent on providing liquidity.