I picked up one of these while it was on sale, even though I already had an F6. I figured it gave me a little flexibility in case I wanted to run a rig FOB and one on stage.
I've only taken it out twice. My experience is that you can't trust rechargeable AA batteries on it - they barely made it through a gig just taking a line signal from a board, I can't imagine how fast they'd drain running phantom to power mics. The 2nd time, I had it running off a USB powerbank and running two mics - it was fine, but cumbersome. I need to test out the lithium ion (non-rechargeable) batteries everyone has been using.