Comment by ancillary

I've been an AC (the person who manages the reviewing process and translates reviews into accept/reject decisions) at ICML and similar conferences a few times. In my experience, grad students tend to be pretty good reviewers. They have more time, they are less jaded, and they are keener to do a good job. Senior people are more likely to have the deep and broad field knowledge to accurately place a paper's value, but they are also more likely to write a short shallow review and move on. I think the worst reviews I've seen have been from senior people.