Have you ever had a manuscript severely damaged by the process of peer review?
by way of example, I can recall one time where the Editor demanded I chop off two experiments..and I did so*.
Otherwise, I'm generally of the opinion that peer review has a positive impact on the manuscript.
*Those figures have yet to see the light of day and may never get published. A shame, but then, we got the paper published and the main point was one of the other figures.