Just to be clear,
the Frontier AlphaTrack is a control surface and not an audio interface. It's basically the transport section plus an "adjustable" track control (meaning that it has one slider that can be assigned to the track of your choosing).
That said, I do own the AlphaTrack and use it in Sonar and I like it. Wouldn't say I love it, though. The main reason I got it was to have transport controls without having to constantly use the mouse. I also wanted it for recording automation, but I've found that its response in Sonar is a bit jumpy, not very smooth. However, that could be a symptom of my own latency issues and not directly attributable to the AlphaTrack.
If you are looking for a convenient control surface, you can't beat it for the price. I'd also check out their TranzPort (
http://www.frontierdesign.com/Products/TranzPort). It's wireless, which is especially handy when you're recording yourself and can't be close to the computer (like at the drums or whatever). Or you could just get a wireless keyboard and mouse. ;-)