I got zoomed about a week ago. After reading reviews I was afraid it was going to hurt pretty bad and I was nervous. But during the procedure I only experienced one minimal "zing." After the process was over, there were some more zings when I would open my mouth to talk. And those did hurt pretty bad, not awful though. And It only lasted into the evening and that was the end of it.
I wish it was less expensive obviously but if you want whiter teeth, it's worth it. Especially if you could get a deal on it. I'm also using the at home whitening trays and those are helping too. I have before and after picture.