Yes, it is.
Just like you, I often like to just switch on a synth an play without having to boot up a computer. To this end the MF2 has a "Mix" knob. In the leftmost position it passes the inputs to the outputs for direct monitoring, which works in stand alone mode. In the rightmost position you'll hear only the USB audio, and in between you can mix between the two.
It still needs power through the USB connector of course, but this can be from just about any USB power-supply/charger - no computer needed. All my computers supply USB power even when not running, so that's what I use to power the MF for my "dawless" jamming.
