The newest version of Jack is available in Jaunty: jack-audio-connection-kit 0.116.1-1ubuntu1. It would be great to get this backported, because the Intrepid version is so buggy it causes serious problems with home recording and music production. Quoted from the release announcement (2008-12-05) at jackaudio.org:
"On behalf of the JACK development community, I am happy to announce the release of JACK 0.116.0. This is an important release, because it fixes all the problems reported with 0.115.6 and now makes 0.109.2 completely obsolete. Nobody should be using 0.109.2 within a few weeks, and even that is only to allow for distributions to update.
"As usual, upgrading to this new version does not require clients to be rebuilt or relinked. Packagers should note that there really are manpages for most of the "tools" clients now (unlike the claim in 0.115.6). These manpages will improve as we get closer to 1.0, as will netjack which remains a hotbed of development activity thanks to Torben."
Thanks, backporters!
EDIT: a silly oversight on my part: the package name that includes the jack connection kit is "jackd." See: http://packages.ubuntu.com/jaunty/jackd
Confirmed; Prevu'd it. Builds, installs and runs as expected. Additional feedback/testing needed.