I have a Fast Track Pro.
Worst, most unstable interface I've ever experienced.
I used it for less than a month and bought my 18i6.
I refuse to even try and sell it because I don't have the heart to put someone through the whole crappy driver thing.
I gave it to a friend just so he could record his ideas and bring them to me when we write songs.
He hates it too but is having money issues. For free it works ok for his little 2 min idea recorder.
 
Mike

I have a fast track ultra. It worked OK. Not super great, and the preamps in it went bad after a few years. It wasn't a huge issue for me, but it could have been.

X1 & X2 doesn't deal properly with the 64 bits latest WDM drivers....but it works flawlessly when running
S8.5 (64 bits obiously) on the same PC.

a) there is a 2 seconds delay before playback when you push pay
b) randon clicks, pops on payback.
c) strnge bhavior of the time window.

it works fine when using the asio drivers; I reported this in the early days of X1.

M

Well here's my take!
 
I use an M-Audio Delta Audiophile PCI soundcard with good old Windows XP SP3 & Sonar Pro 8.5.  To date, I've never had a problem or stability issues but will shortly be switching to a new Windows 7 64-bit Pro rig so we'll see how it fares.
 
However, I have to agree with the points already raised here that I used to love M-Audio until they got bought by Avid which was the worse thing that ever happened as the support was terrible & if you wanted quick phone support, you had to pay a stiff charge upfront!  I also found them very slow to update drivers.
 
In fact, I used to have a number of their interfaces like the MIDIsport 2x2, 4x4 & 8x8 but got fed up with waiting for driver updates so I sold the lot!  Well, I've still the 2x2 as that one seems to get driver updates in a reasonable time.  I exclusively use Edirol/Roland UM series interfaces now & even for their discontinued products, they were still quick to update all the UM series to Windows 8 drivers.  How's that for customer support & loyalty?  I've always felt that you can trust good old Roland.
 
So on that basis, I won't buy another M-Audio product again!
 
Saying that, as they've been bought out by another company, I may give them a go & see if things have changed otherwise, it's an essential avoid for me...

I have a Profire 610 and seems to work OK but I wish they would release a new driver for Windows 8. I was just getting ready to post that they are too slow to update drivers and that I would not get another m-audio device. However, before I posted this, I checked their website and I was surprised to see a new driver released 16 days ago. Downloading and installing it now

Thanks for the input guys.  I think I might stay away from this interface.  Although $269 is not a bad price for that many ins and outs.

I am using a Delta 66 PCI card that I have used for years and it works just fine with Windows 8 with the exception of a few minor nits. Sometimes an application won't release the driver so if I start another application it doesn't see the card. Other than that nit, I am getting 64 Samples rock solid on my i7 Windows 8 machine using the Windows 7 x64 driver.
 
That being said, M-Audio is like molasses in releasing new drivers, especially for legacy devices. They originally abandoned the MidiSport 2x2 in favor of the "Anniversary model" which had different Windows 7 drivers. The forums were screaming with pissed off people so they finally released Windows 7 drivers for the original MidiSport 2x2.
 
My next card is going to probably be an RME because I use a lot of soft synths and I can feel the latency even at 128 samples so it looks like an internal card for me as I don't think I can get reliable 64 samples with USB and I'm not interested in Firewire.
 
Bottom line:  I would avoid M-Audio if I were you. It's not the same company it used to be and your chances of buying a product that will become an orphan are high.

My FireWire Solo was getting a little squirrely on me about a year ago. I decided to switch to USB and went with a Focusrite 8i6; really like it.

Funny how a lot of reply's are from people with the Delta PCI cards, One would assume they are a completely different piece of gear than a M audio Ultra which is a plastic box.
I have the Fast Track Pro and I can only use the SPDIF. The pre amps were way to noisy for me. There is this hi pitched "scream" in the headphones too. I gave it to my son to play with and he uses it to watch movies from his laptop. I think the unit was basically a dud as I know lots of people did not have issues, but that brand is off my shopping list. 

I have been using the 1010lt for years now with little problem except for a time when M-audio needed to update their drivers. That was a pain, but they finally got around to creating the needed drivers. The problem was noise filtering in after a period of time of recording. I have been using the card successfully for over a year now.
MJ