I am generally comfortable as a peer-reviewer, but usually that is for more pop science articles or short stories as opposed to harder science articles like these. I think that articles like these are much more difficult to review like I normally do, especially because we aren’t necessarily editing for ideas and content or word choice or what have you.
I found that in reviewing my assigned articles, I was trying to think back to writing my own article. Whether or not I had included my own thesis statement, or if I had supported the side opposite my opinion as well as I had supported my own side. All in all, I think that peer reviewing, especially in this context, does make you think about how you are as a writer yourself, and that reflection often is the basis for growth.