I found the process of peer reviewing to be very beneficial for me, it made me reflect on my own proposal. One thing in particular was my explanations of terms and processes. I read one paper that did very well in defining all the pertinent items. This made me think about my own and re-access the quality of my work.
I think it is also helpful to get feed back from your peers before turning in a final. It makes it feel less stressful for me. I should mention though that I do not mind being critiqued or critiquing others.
Lastly, I enjoyed seeing the very broad range of interests between my peers. I like expanding my understanding of the microbial world and this really helps to get exposed to more fields.