Well, I finally have a complaint about the 521. I like to use the speaker phone for hands-free writing etc. When I do, I often get a lot of feedback, echo, bad sound etc. I think I finally figured out why. Nokia put the external speaker on the back of the phone very close to the microphone. If the volume of the external speaker is turned up more than a smidgen, the microphone picks up the sound of the speaker and creates the problem. Anyone else noticed this?