The bummer about Balance as a "mixer" is that it doesn't mix channels. In live monitor mode, you can hear the output of your computer (coming over USB) mixed with ONE selected channel on the balance, and that's it. Well, technically two inputs if they're mono... but you get my point I hope. It doesn't actually mix the 4 sets of inputs in any way at all.
I had kinda thought it did when I bought it, and was surprised and disappointed that it didn't... but I decided I liked it anyway so I kept it.