I got this for my son to mic up his trumpet for use in his band. The power supply / DI adaptor is extremely well made and feels like a professional quality item. The mic and its clip feels vulnerable, but we have had no problems in over 12 months of (less than careful) stage use. Battery life is excellent.
I have only heard it in a live situation in a pop/ska band, where it has always sounded very clear and natural, with no hint of harshness, clipping or overloading. Feedback was also not a problem, provided the usual precautions were taken.
We found that the lead from the mic had to be left very loose as the mic picked up mechanical noise from the valves if the cable was kept neatly against the instrument (probably vibrations travelling down the cable to the mic capsule).
The only critiscism applies to wired mics in general, and it is that to put the trumpet down and play another instrument, it is necessary to unplug the mic from the powersupply/DI, and you can't use a 'normal' trumpet stand with the mic clipped on, so that usually needs to be moved, too. This has led to some frantic moments on stage occasionally.
We bought it not knowing what to expect, but I have to say that I'm very impressed with it, and would recommend it for a live situation (with the caveats about wired mics in general).