I bought this unit mainly because it offered insert points on 4 channels before the audio headed off to the usb software in my laptop.
I hoped it would be "4 in, 4 out, 4 inserts and USB"
However it is not!
Outputs 3 & 4 are only available after the usb interface and only if you are able to use computer software that allows 4 simultaneous in/outs on USB.
I use Audacity (yeh, I know, but it's great for what I want to do) which doesn't allow the use of ASIO4ALL or the M Track drivers so this know means that I need to purchase ¤400 worth of Cubase/Sonar or equivalent just to use the M Track.
I have looked through many reviews of this unit and not one of them, even on the M Audio website, mentions this serious failing.