Note that MOTU are hostile to Linux and do not support our effort in any way. If purchasing a new device for use with Linux, please seriously consider purchasing one of the devices marked as having "Full support" on our "Device support" page - this indicates that the vendor is actively helping FFADO in some way.
The "mark 3" MOTU devices released during 2008/9 come with substantial changes to the device control protocol. A picture of this is being built up as owners volunteer information but it's not possible to guess as to when FFADO will function with these devices. The process will be greatly accelerated if someone were to donate (or even loan) a "Mark 3" device to the FFADO project to allow me to analyse the protocol efficiently (please contact jwoithe via the ffado-devel mailing list if you're interested in doing this - I'm in Australia if that helps).
Update, 22 May 2010: I have been loaned an 828mk3 for the last few weeks. It's had to go back now but it's given me enough to start working seriously on the "Mark 3" support and the beginnings of this are in svn (see revisions between r1831 and r1836 for example). It looks like the 828mk3 will be the first "Mark 3" device supported since that's what I've had access to. No ETA on this yet, but progress so far has been good. There's a possibility that I might be able to get the unit back again in a few weeks; if that happens development will possibly come to fruition quicker.
Update, 2 September 2010: audio streaming has been demonstrated on some of these G3 interfaces over the past few months, which means jackd can be used to get audio into and out of these interfaces under certain conditions (when testing this please make sure you're using the most recent svn snapshot available - r1882 or later). There is a report that the Ultralite Mk3 and the Ultralite hybrid (in firewire mode) are mostly working. The 828 Mk3 streams audio for most combinations of optical port mode settings (although some are yet to be tested). The Traveler Mk3 streams audio at all sample rates so long as the optical ports are turned off. Work is continuing on making the optical port support better on the G3 devices which have optical ports. ffado-mixer currently does not work with any G3 models. The protocol is pretty well understood; I'm hoping to find time soon to start adding this to ffado.