Nicely done for your first PS portrait. Here's the first few things that leapt to my mind.

- Proportions of the features look a little off. I think in trying to capture his smirk you may have shifted the mouth too far to the side. Also, it seems like there's a little too much space between the features and the hairline/side of the face on the right side. It makes the face look a little too broad.

- His posture is a little hunched, like he's at an awkward middle space between having his head up straight or having it down and leaning forward. If you didn't use a reference for the pose I'd suggest doing so. It's very helpful.

- The clothes look pretty well laid-out but they're a little stiff. Putting some subtle folds in there (in the shirt for example) and making the existing lines a little less smooth and regular should help. Again, a reference is invaluable for trying to figure how folds should lie.

You did a great job with the limited colors, shading and values are pretty solid (although going for stronger contrast could give it more drama) and I think you definitely captured that retro cool feel. The open collar and loose tie is a nice touch.
Maybe you could add something futuristic-tech looking to the wall behind him to cement the sci-fi aspect. It would also provide a nice contrast to his 60's style clothes.

Hope that's helpful.