LiveJournal's felt damn fast today as a result (except when a DB exploded).
Next up: HTTP/1.1 chunked responses, when needed. (which is harder, because once we speak HTTP/1.1 we have to understand 1.1 requests, which I'm not sure we're quite ready to do....)
For now almost all of our responses have content-lengths, though, so chunked responses aren't really needed.
Props to marksmith for the persistent connections support.