avid just released a new driver with windows 8 support a few days back. the link is http://avid.force.com/pkb/articles/en_US/Download/Fast-Track-Ultra-Drivers

oops... they don't work in asio mode with sonar... phlegh.  fine in ableton live, reaper and reason...
anyone get them to work?

I'm using the older driver in Win 7 and Win 8.  Seems to be OK in both, although my Fastrack Ultra 8R is my backup unit.  My main unit is a Roland Octa-Capture.

Yeah the older driver was working for the most part in sonar and flawlessly on other daws. The new driver finally fixed the 64 sample latency issue in asio mode. Unfortunately wasapi mode and wdm with the new drivers perform poorly as well.

swamptooth
avid just released a new driver with windows 8 support a few days back. the link is 

I too have tried to install the new driver but can only get sonar to use wdm/ks driver mode. ASIO is not available. Is this yet another X2a bug?
Or have Avid written a bad driver.

I would say its the Maudio drivers (which is no longer owned by Avid)  MAudio is now owned by "in Music Brands" which also owns Alesis, Akai Professional and other brands.  http://www.inmusicbrands.com/
 
Keep in mind, older drivers worked and the new ones don't - that points the finger at the driver.  Like when a software program does not work, its not a Windows OS problem its the software program - Windows does not have to be compatible with the program, the program must be compatible with Windows.

fireberd
I would say its the Maudio drivers (which is no longer owned by Avid)  MAudio is now owned by "in Music Brands" which also owns Alesis, Akai Professional and other brands.  http://www.inmusicbrands.com/
 
Keep in mind, older drivers worked and the new ones don't - that points the finger at the driver.  Like when a software program does not work, its not a Windows OS problem its the software program - Windows does not have to be compatible with the program, the program must be compatible with Windows.

m-audio does not support the product anymore, it's an avid legacy product and they released the latest drivers.  i don't think it's the drivers... it's a sonar thing because the new driver works fine here in cubase, reason, reaper, live and fl.  sonar is the only program that does not recognize it thus far.  my guess is that it's because the new driver is native multilclient asio and cake is somehow incompatible with mc asio drivers.
 

I installed the new driver this morning.  My Fastrack Ultra 8R tested OK in both Win 7 64 bit and Win 8 64bit with Sonar X2 64 bit.  I have a dual boot system so its the same hardware with both Win 7 and Win 8.  I did a quick recording test and it was OK and playback is OK, ASIO mode.
 
I've also got ProTools MP9, but I didn't test with that, as I don't have it currently installed. 

Has High-Performance mode been added back?

@jim - yeah, sure has.  works fine in other daws set to 64 samples for recording and playback running all 8 channels.  do you have an ultra or ultra 8r?  
 
@jack - 6.1.8 drivers, right?  are you running sonar in 32bit or 64?
tested with stand-alone dimension, z3ta+2 and rapture - no luck.  all native-instruments stand-alone devices work fine.