There is also an excellent post by Brad Hedlund on his blog diagraming and explaining supported and unsupported designs for routing over vPC peer-link:http://bradhedlund.com/2010/12/16/routing-over-nexus-7000-vpc-peer-link-yes-and-no/

the peer-gateway command does like you stated: it allows the active router to forward packets it receives that are destined for the MAC address of the physical interface of its HSRP peer.In theory, yes, everything should have a destination MAC addres...