What am I missing here? It looks sloppy and disproportional to me.
I don't know, but this is one of the best fits I've seen in a day or so. The jacket definitely has some features which are not on your normal straight forward wind breaker that make it stand out. Everything fits really well. He's a very skinny guy and dresses to his body type very well.
Not getting "waiter" at all - that is excellent. The full-cut pants look really great, and the mandarin collar is fantastic. Simple, but really, really, really good. It helps that the photo context is perfect. I think you should start adding some fabric close-ups, though.
a slouchy DB jacket would look really good on top of it all, I think - MMM has done a few, and *duh*yohji*duh*
maybe you could do something in the way of some different (funkier?) shoes to push away from the waiter-esque vibe. It does have that resemblance a little but still looks cool. btw... I have a few Mandarin collared shirts and always dig them!