I don't think so. But I'm not sure. I'd sure like to be sure.
If I had (1) time to hammer out a comprehensive spec for content
negotiation, or (2) more time to hack on a browser to work out these
implementation issues, I'd feel more comfortable commenting.
I expect to free up some time (somebody's time, anyway) for this in
the near future (probably after Xmas) but until then, I'm afraid I
can't help much.
We've discussed the issues ad-nauseum, and my only conclusion is that
it's not so simple as it once looked. I encourage folks to experiment
and report their results. (As an example, take a look at the HTTP-WG
discussions on multiple-transactions-per-connection in HTTP. Plenty
of performance numbers and such. Good stuff.)
Dan