Those of you who may be <64kbps Ogg experimentalists may want to consider checking out John33's OggDropXP, which has the downmix and resampling switches enabled, as well as a few other nifty features.
I've been getting encodes down to the mid 30's (kbps) suitable for modem streaming (downmix & resample), so streaming Vorbis is a reality for me at least, even before the optimisations. It sounds pretty reasonable too!
Get OggdropXP here:
http://rc55.grooblehonk.co.uk/users/rjamorim/index.html
Ruairi