I think currently the most convenient thing is to use HTTP internally and have something on the front end that does SPDY between end-user and server.

Seems like SPDY would be beneficial as a replacement for HTTP everywhere though, because the payload for each request is smaller. However, SPDY seems to be optimized for the longer, higher latency, and slower connection between user and server rather than the faster internal connection between load balancers and servers. Finally, all SPDY communication is encrypted via TLS, so that process might add to a slowdown between internal systems.

Guess we'll need to benchmark it and see! Looks like Apache and Jetty are the only supporters of this so far. And I'd never us Apache as a direct front-end.