I agree with both above posts. The forarms on someone so muscular shouldn't taper to be quite so thin so quickly. And the upper arms should be lengthened juuuuust a little to help the overall proportion.
What immediately jumped out at me was the relationship between the upper and lower body. I know that you want him to look bulkier up top, but there's a problem. Some of the structure of the upper body is dictated by the ribcage... you can see how it shapes the regions just under the pecs and in front of the lats. BUT... no matter how many weights you lift, you cannot make your ribcage get a lot BIGGER than it starts out... you can build muscle on TOP of it, but the bones themselves will stay the same size.
So your dude looks like he's got a size XXL ribcage balancing atop a size S pelvis. Which never happens in real life.
If you're going for realism, shrink the ribcage area and scale up the pelvis area just a little to find that happy medium. Then I will love it.
A little more analysis of the collarbones would be nice, too.
Got any wireframes or rear views for us?
Wonderful work. Thanks for sharing.
-Steve