Instruct: Classify Amazon reviews into positive or negative sentiment
Query: I agree with negative reviews

It is really frustrating to spend good money on something to have it flake out after the warranty runs out. I have had similar problems like those described. The unit worked very well for about a year and a half and then the buzzing started in earnest. Previously this meant that a quick cleaning was indicated, but now nothing will eradicate the buzzing. We had to move it to the spare bedroom (where it doesn't do much good).