The lettering distracts me.
Looking at this with the analytical eye that (I think) I'm gradually acquiring, I find that I'm not inclined to take it as a literal depiction of reality. After all, in reality, peoples' faces don't blend into the whiteness.
I see the "blinding whiteness" behind the subject, and the highlights merging into that brightness. At the same time, the rest of him is much darker, much closer to reality. Overall, there's heavy contrast between the background (wherever the subject is, figuratively, I guess) and the way the subject appears. Also, I find it interesting in this light (no pun intended) that this is a nude, which nobody has pointed out yet.
I won't get too much further into interpretation than that, partly because it seems to me that the topic is the composition, rather than the message; and partly because I probably don't know what the heck I'm talking about.
Anyway, considering what the "message" may (or may not) be, I think that the horizontal format is important. Probably critical. If you turn this one on its side, it just wouldn't be the same. Also, the way he's placed in the image leaves me with the impression of, maybe not advancing, but almost as though he's just come around the corner and is wondering what I'm doing... perhaps as if I'm supposed to be or have been following. Also, I'm not quite sure why this expression would be described as "vacant." Subject is looking at viewer, and is clearly thinking something. To me, "vacant" means "catatonic," or something similar--at the very least, detatched from the present circumstances.
Anyway... Like I said, I probably don't know what I'm talking about, and I'm probably reading too much in to it. So, I'll sum it up: this shot needs to be horizontal, IMO, just as the waitress or cigar-smoker do.
My two-an-a-half cents, and you get what you pay for.