From 20 or 30' away, as I used it in a conference room, it worked very well and improved the audio recording compared to the recording function of the camcorder (which picked up all the surrounding paper shuffling, etc).  The downside to using this (or any lapel mike) was it doesn't do as well as picking up surrounding conversations - such as questions during a face to face conference room training.  In that case, I simply had to remind the key speaker to repeat the question and then answer it.  There were some big advantages over the 20' wired lapel mike I used - mostly the absence of the cable.  There there was little difference in audio quality.  I also did a brief test recording audio in separate rooms, with a closed door - and while my test was far from complete, the audio was still good.  I think some of the concerns are the claims that this can work from 300 feet.  I can't say that it does or doesn't.  The 9V batteries lasted a good 8 hours each.  It was unclear to me (probably because I didn't real all the directions) if there was a warning to change the batteries or not (I'll have to go back and check) but, for my basic needs, this worked fine and the audio quality was good.  Never had to change channels.