Hi Jason, that is a really stonking portrait shot. Awesome. Love the tilt of the head and the expression. Really lovely.
Lighting: with one tiny caveat, it's perfect for me. It's a slightly unusual setup but for me it works really, really well - perhaps because of it being different. Maybe rein in the highlight a tiny tweak on the forehead, above the right corner of the glasses frame but that's really quibbling (and not my caveat, btw). Half in shadow works perfectly: there's enough detail but also a good amount that's hidden. Nice. Lack of offputting shadows under the chin etc. really works - did you need a reflector at all underneath?
Details on the eyes, hair, face, frames etc. are all spot on. That right eye in particular is fantastic... they are the windows to the soul and your photo is wonderful in that regard. Nice catchlights.
You've dealt with the specular reflections on the frames well - just enough to suggest gloss without distracting. Perfect.
So... this caveat... well, it's a tiny one. The shadow on top of the head is both puzzling (not sure how you've managed it!) and slightly distracting for me. To be honest, this is a tiny quibble on an otherwise nigh-on perfect shot. To be honest, I'm curious as to how it's happened given the direction of light source: was the flash snooted or gridded? I see in the flickr tag you've marked it as "natural light" in which case I'm even more puzzled as I'd expect some wrap-around to light the top of the head!
Super, super shot.