I just finished trying the SCALA-500. For me, this was the worst of a bad lot. It has a slight echo. I can mentally tune it out, as the delay is not toooo bad. People that I call say I sound like I'm speaking through a fan, my voice is chopped and "robotic" sounding. this must be the noise cancellation software trying to compensate for my noisy bar. Sometime when I make a call, I get a feeback squeal that is loud enough to be painful! That seems to happen about once every 4 calls. To fix it, I can hit the MFW and jog the volume down a couple of notches, then back up and the squeal is gone. Still. I can't live with that.
Today I'm taking it back and going back to the Jabra freespeak 250, which is what I started with before I launched a crusade to find something more comfortable!