Thought I'd add my two cents to the thread based on my experience so far with this device. Back in April I was shopping around for an 8-channel audio interface compatible with Vista 64. After some research it looked like my laptop's chipset has issues with Firewire (both the built-in and with any add-on cards). I did a test install of the Fireface drivers which did not play well with my configuration. So that pretty much limited me to USB 2.0.
The Fast Track Ultra 8R was actually a bit of a pleasant surprise. I was prepared for the worst--driver issues, crashes, glitchy audio, that kind of thing. It installed with minimal hassle, and it sounded great once I figured out how to configure Sonar 8 64-bit to use ASIO instead of WDM. I also gave Ableton Live a try (side note: the demo version of Ableton Live only supports 2 channels of recording, so unless you already have software you can't use all 8 channels right out of the box). It works well but it's not really what I'm looking for. Cakewalk has a demo download of the 64-bit version of Sonar 8 so I was able to try things out before throwing down the money.
There are three issues I've found with the Fast Track Ultra 8R. The first is that it has trouble with certain USB ports on my laptop. The second is that my computer crashes when I lift the lid IF I unplugged or turned off the interface while the lid is shut. The third is that the channels show up in Sonar as stereo pairs (channel 1 left, channel 1 right, channel 1 stereo, channel 2 left, channel 2 right, and so on). I want them to have labels that match the numbers on the front panel.
When it's plugged into either of 2 ports on one side of the computer, the audio crackles and pops. If I plug it into the port on the other side of the computer, it works great. I suspect this is a problem with the way my laptop was designed--perhaps the ports on the one side are shared on a hub with the trackpad, keyboard, and other devices. Solution: Try each of the USB ports on your computer until you find the "good" one.
To solve the second issue, I have to unplug or turn off the device with the computer fully awake. It's like the old joke... Patient: "Doctor, doctor, when I pull my lower lip up over my head, it hurts!" Doctor: "Well don't do that!"
For issue number three, there has to be some registry hack, configuration file, or some such method for fixing the channel names. I haven't found it yet, but I'll post it if I do.
The sound quality is pretty good. The preamps are a big step up from my junky old Alesis IO|2. I lifted the lid (don't tell M Audio) and found that each channel has a THAT 1510 preamp IC. A bit of research on the web shows a few rather expensive boutique preamps also use this IC, which gives me warm fuzzy feelings. Picky stuff: The preamps get quite noisy at the highest gain setting.
Each channel has its own 24-bit analog-to-digital converter (AK5386) which is rated for 192KHz but only used up to 96KHz. Likewise, each output channel has a separate digital-to-analog converter (AK4384). They are all chained together to the DSP (SAM3308B from Dream), which handles the built-in effects (not so great sounding, but fine if a singer wants some 'verb on the monitors) and the data processing for the USB 2.0 interface. I'm glad M-Audio decided to go with this arrangement instead of some buggy all-in-one USB audio chip. The 64-bit driver support is in beta but it's worked out pretty well for me.
The headphone amplifiers are a bit bass and low-mid heavy so I've had to mix with that in mind. The amplifier ICs are NJM4556 devices from JRC--not terribly good, but better than what's on the IO|2. Fortunately it's easy to connect an external headphone amp.
The Fast Track Ultra 8R is no Aurora, but it's got a good bang for the buck.