First Im sure you already know about having 2 people in the shot so Im not gonna go into it.
Composition: Everything seems a little centered to me. Having the main subject off to the left side may have improved the composition slightly. Maybe getting rid of some of the empty space at the top also may have helped.
Technical: The shot overall looks out of focus. I know the light blurs are intentional but the main subject seems a little blurred. The lighting seems just fine for the subject and I can definatly see the hidden waldo.
Overall: Original idea but having two people in the shot knocked your score down tremendiously.
I see the hidden person, but as the hidden person was supposed in "an otherwise personless photo" I don't think this meets the challenge. Also, the motion around the very visible person (long exposure?) is a bit distracting.
I'm sorry, in my mind, you did not meet the challenge. You obviously disagree, otherwise you wouldn't have entered this shot. I suspect your "Waldo" is the person in the background to the right of the dude in the center. Anyway, I'm sure you've already heard that part from many others, so let me just give you some feedback on the photo itself. You've "broken" some common rules here, but I think in your photo it actually works. The subject is centered, and the background is rather busy. However, the background is still mostly separated from the subject, and I think that's what works. Also interesting that the lights in the background are obviously moving while the guy is not. That tells me that this is a longer exposure, and for that, the guy is actually pretty sharp and focused, even though not perfectly. Did you hand-hold (the "shadow" on the baseball cap makes me think you did)? Could you have used a tripod to get this really sharp? Nice catchlights in the eyes and good skin tones.
I get it. Took me a sec, but I see the "hidden" person now. This is a neat shot. The focus is a little hard on the eyes, but I realize it was done on purpose, and done well. The color is nice. The black coat blends in a bit with the dark background, but I don't feel that that harms the photo in any way. Overall you have done a good job with this effect. Good luck in the challenge.
I see the hidden person, but you do know that you're supposed to have a hidden person in a shot with no people. right? I only subtract one, but I bet it affects your score. Too bad cause it's kinda cool.