No, but Steem includes the same kind of exchange functionality that Bitshares has, only limited to the STEEM:STEEM DOLLARS pair. Hopefully steemit.com will offer trading in this pair come July 4th, but if it doesn't I'm sure it won't take long for it to appear.

Regarding OPEN.STEEM:USD on the Bitshares network, I noticed Xeldal's bot enki has started trading in several OPEN.STEEM pairs which should help liquidity there.