First of all, the new FFADO packages currently fail to build on Maverick, because of a Python policy violation (bug 586821). A fix is underway, but I didn't want to wait and built a quick-and-dirty workaround package. If you like workarounds too, feel free to install libffado binaries from my PPA.
Second, to use the new firewire stack, FFADO needs at least libraw1394-2.0.5, which is also missing from Maverick. Hopefully the new version will be merged or synced from Debian soon (bug 586918), but if you don't want to wait again, you can install the package from my PPA as well. That will work.
Next, the old firewire stack has to be blacklisted. Simply edit /etc/modprobe.d/blacklist-firewire.conf to look like:
Finally, run "sudo update-initramfs -k all -u" and reboot. That's it... One thing to remember is that Juju creates device nodes with /dev/fw* paths without write access by default. This is easily fixed by a little udev tweak (example configuration may be found here).
Just to be safe, I also updated my rtirq settings to increase the priority of firewire_ohci IRQ service. It will not make things faster right now, because rtirq requires a realtime kernel, which has not been updated for Maverick (yet).
I like the fact, that all existing JACK applications work without any extra configuration or recompilation. This includes QJackCtl, Qtractor, SuperCollider, JAMin, energyXT... Only Renoise started to hang and produce bad noises, until I switched the "Realtime audio CPUs" parameter to 1. Most likely it has something to do with JACK's own multicore support.
Some applications may also display strange port names (like firewire_pcm:0500000000000000_Unknown5_out). Luckily, JACK provides port aliases in the "system:playback_N" form. Aliases seem to work transparently for connecting/disconnecting ports, but QJackCtl will only display them if you set the appropriate option in the setup dialog.
Audio streaming is generally stable most of the time, but I've heard glitches with both the internal firewire controller (Ricoh R5C832 rev 05) and an ExpressCard controller (Texas Instruments XIO2200). So, I would not recommend performing live with Maverick right now. Nevertheless, it is great to see the progressing firewire audio support in Ubuntu. Juju migration is one of the Maverick development targets, and there is a blueprint to track the process.