So, I got a lot of help on this during the whole process (from sketch to finished product) from the good people here in the Critique forum. Thanks to: novenus, sve, Infinit, Roningenius, Grendel Grack, biotwist, rabeat, FlameRaven, Wasker, and JoeSolo.
There were a couple very good suggestions that I didn't end up following, for example, that his pose and expression aren't very dynamic. Also, his head is shaped... incorrectly. I agree. I'll pay special attention to those issues in the next thing I do... if I ever get around to doing anything else I've included some details at 100%. Anyway, it's been a very fun process, so cheers all!