From the ffado site (for those playing along at home):

After far too many delays (both technical and logistical,for which I apologise), practical progress has finally been made on the FFADO RME driver.

In short, the driver is now ready for wider testing, although there are some important limitations and cautions to keep in mind before proceeding. Read more for the details.

• If a non-zero verbose level is selected using the "-v" option, a 0 dBFS 1 kHz sine wave will be output on the left phones channel. This is to facilitate debugging of audio timing. If you have headphones or monitors connected to the phones output, please do not activate verbose debug mode without taking appropriate precautions.
• The level produced from the phones (aka monitor) output is very high from this device and the front panel "ph" level control does not affect the level being sent by the computer. Use headphones with extreme caution to prevent inadvertent hearing damage, especially during initial testing and/or if no software volume control is in operation.
• You will need the latest subversion snapshot of FFADO.
• Ffado-mixer support is still rather limited and contains only a small number of controls (now the streaming system seems to be working I expect to expand this soon). In particular there is no user access to the onboard mixer controls: however, ffado sets these to a 1-1 mapping which should do for testing.
• Meaningful testing is probably limited to the Fireface400 for the moment since that is the interface I have been testing with. I will test with with a FF800 in due course - most likely after I've got a more complete ffado-mixer working for the ff400. In the meantime, it is almost certain that the driver will not run with a FF800 yet.
• I've been testing exclusively with jack1 and the old kernel firewire stack. In theory jack2 should work just as well, but I have seen reports over the last couple of weeks which suggests that there may be a problem with ffado in the latest jack2. YMMV. Similarly the new kernel stack should work but I have not personally tried this yet.

To provide feedback on your experiences please subscribe to ffado-devel and post your findings there initially. If extended discussion is required we can take things off-list if appropriate.

My testing to date has been mostly with 48k and 44.1k rates. I have fired 96k and 192k up and had them work for short periods of time so hopefully that's a good sign. Finally, for initial tests it is probably wise to stick with fairly large latencies: I've been using "-p 1024" and "-n 4" options when starting ffado via jackd.