To Pd dev -
I've pushed what I think is working support for multichannel signals. Many objects haven't yet been adapted to deal with them, but there are enough to at least test the concepts: lop~, send~, receive~, and (ugh) clone are multichannel-aware, and new pack~ and unpack~ objects are provided to combine and split signal channels.
I've put a couple of example patches on http://msp.ucsd.edu/tmp/multichannel-tests.tgz ... the interplay between multichannel inlets and outlets and clone are sometimes amusing.
cheers Miller