I don't think I've ever attended a formal peer review.
At work this summer, we had "inspections", but the process was much more well-defined. Reviewers would mark defects
before the meeting independently, the person would either fix them or make a comment saying the issue should be discussed during the meeting. It kept out the long, drawn out debates that result in pretty much nothing. It was a fairly painless process. The meeting for my code, which was about 10k lines, only took 45 minutes -- and that was with the principle engineer there.