I've been using the amplifier and like it a lot. As for problems, so far no big ones, just getting used to it.
The feedback noise only occurs if the volume is turned too high for the surroundings, or, if I bend forward and the microphone comes too close to the speaker. One thing, though, is turning up the speaker to be heard over ambient noise in an enclosed space (my little car) can result in the feedback squeal, I'm still figuring out the best way to overcome this. Yesterday, I unclipped the belt strap holding speaker to my waist, and just laid the speaker between me and the other person in the car, so it was facing up toward the soft cloth ceiling, rather the hard sound-reflective surface of the dash board.
The dog pays good attention to it, probably because its still my own voice. He was really interested at first, maybe because he could hear my voice coming from my mouth as well as the speaker? I don't know. He was really cute, would cock his head one way then the other looking back and forth from my face to the speaker.
The microphone is super light. only 2 ounces. Its not noticeable at all. Even if it were, what with so many people wearing the bluetooth earpieces for their cell phones, I don't think it would draw much attention. (and who cares anyway?) Here's a couple of photos of headset