Bitcoindark looks interesting.. that very well could be one of the best PoW coins out there. I like Bitmark too.
IMO PoW is bad though.. a lot of waster processing power and electricity. Also, once specialized hardware is built they will likely suffer from centralization due to economies of scale.
I don't think it would be a horrible idea for bitshares to consider a PoW coin though to bring more people into the community. There are a lot of people with sha256/scrypt mining hardware. However, I think that is kind of what Bitshares has been lobbying against all this time, since it uses so much electricity to protect the block chain isn't sustainable.