Show me a networked data store which does better on the same hardware. (FWIW, with trivial keys and values, kivaloo gets significantly more operations per second.)

default 128 MB memory limit on kvlds. this can be changed i suppose? i hope docs will be coming.

Command-line option to kvlds, documented in a text file in the kivaloo tarball.

services requests upon it from a single connection; and a request multiplexer (mux) which accepts multiple connections and routes requests and responses to and from a single "upstream" connection. does this mean it support multiple requests in one round-trip?

Yes, and responses can come back out-of-order, too.