Avahi 0.1 is due in the next few days. The last missing piece is a simplifying C wrapper around the DBUS API. Though Avahi is currently pre-0.1 it is already quite complete and mature. To put it with Ross Burton: "... this doesnt count as 0.1 because it has docs, man pages *and* works"
Unfortunately python-dbus has quite a few bugs which make it very difficult to code with. e.g. it doesn't handle sending empty arrays, fails to send byte values and so on. It is difficult to work around all these issues, therefore the Avahi client tools will not work with an unpatched python-dbus. You need to apply this patch (applying to 0.35.2) to fix at least the byte value bug to get them working.