My first impression of IO2 was bad - I listened through headphone out, with my trusty headphones. Trebles and ~3-10kHz are accentuated, making your ears ache after a few minutes of listening. Turned out it was a mistake to do so. Connect it through your amplifiers s/pdif coaxial input, and you are suddenly in heaven. Sound is perfect. So what is that headphone input good for anyway then?? You can use it to monitor your recording without latency, mix the USB/input signal so you dont need to stress your cpu with monitoring (and anyway, normally this would be unusable due to latency).

There is a small bug that it cannot function if you put your PC to standby and start again, noisy clicks are starting to appear. Just boot your machine or dont allow your PC/Windows to go to standby, and all is well! I dont think Alesis will ever fix this, so its up to you if you can live with this little glitch or not. For me, all the robustness and quality features of this box are more than enough to compensate.

One minus for the bad headphone out, otherwise it rules.