I used one for about a year and really liked it a lot. Perfect for stealthing. It is a bit thin sounding so it works well with mics like the AKGs. I would caution you against using it with hot mics (like the Gefells) because the mic preamp overloads in loud concerts with hot mics. A pair of attenuators may help in that regard.
Great unit, though. Rock solid and I never had a problem with it once. Shorter than advertised battery life. The label says 8-9 hours, more like 5-6 under normal use.