"I love working with you. Two things that I think set you apart…
First — you give me your honest opinion on candidates. If they're so-so, you say so. If you love them, you say so. I never have the feeling with you that you have anything but my best interest at heart. You use all of your (very considerable!!!) people skills to find the best match and don't spend time trying to fit a round peg into a square hole.
Second — you just 'get' the business. When I say 'apps engineer,' you say 'Yep, got it.' And you do. It's soooooooo refreshing.
I guess a third thing… you have a supernatural ability to read people. We click well. You understand me and what I'm looking for. You also seem to really understand the candidates. It's your superpower. I hope you always use it for good, not evil!!!
... It's an absolute pleasure to work with you."