In my graduate school program, after we do a rotation in a lab for a few months, the professor evaluates us and we have to read it and sign it. There are a bunch of things to rate us on, then a comments section. I blushed reading the comments that my last professor wrote! He said I was a strong independent scientist, motivated and organized, interacted well with everyone else in the lab, and that I understood our field really well (a field that I had NO experience in prior to being in his lab). When he handed it to me, he said they'd be "delighted" to have my join the lab for the rest of my graduate work. I had a smile on my face for the next hour!
He's a pretty famous guy who does incredible work, so hearing that from him meant a lot to me.