I've been using this for live playing (together with a ATM350) and home-recording with different mics, for over a year now. Only good things to say (it could have one or two improvements, but minor ones). The preamp is fairly transparent. Some users report a hiss, but I couldn't reproduce it. It's probably related to high gain switch, so be careful with it. the send/return loop is well balanced, no problems with impedance, noise, hums, super clean, really. The real strengh in this little box are the mixing options: with a 3pos toggle switch you can choose different mixing options between dry and wet (S/R loop) and have dedicated level knobs to it. The amp output is separated, so you can adjust the output of a guitar without affecting the mic level. However, no mic output level, only input - this can be limiting with some microphones. Also, the aux in doesn't have a level - so you'll have to control it in the unit you're plugging in - and it doesn't go through the S/R loop - this is perfect for playalong backing tracks.
Will keep using and if it breaks (I don't think it will) I'll just buy another.