Wow, that looks awesome. It seems a bit red to me and there aren’t any imperfections on it, but it’s still pretty close to photoreal. One problem with the image itself, though, is some of the shadows, namely below his lip and eye, and also around the left side (our left, his right) of the face. You may want to look into that.
Yeah, I don’t know why those happen, they only appeared with the specular ramp shader I think. I’m about to start enhancing the bump map to add wrinkles and stuff like that, so hopefully I’ll have something good soon.
Nicely done. Looks great.
The scale of the bump seems to be a little too big IMO. Try scaling that so it looks smaller and I think you will have it.
You should play with some blueish Veronoi cloud textures set to very low colour values, so you can just see them, to simulate blood vessels in the skin.
BgDM
I thought it looked a bit rubbery at first but I couldn’t figure out why. I think it might be because of what BgDM said about the size of the bumps. But the specularity and colours look good and the model looks excellent.
The thing about the bumps is it looks like you used stucci noise. Looking at the skin pattern on my hand, maybe voronoi noise would be better?
I had a go at adding blood vessels with the veronoi noise as suggested (I never even knew about that hehe). The work before was just a couple of texture maps done in GIMP and some ramp shader use. I originally intended to do all the details like that, but the gimp can’t get the swap file to work, so I can’t really do anymore work on that skin grrrr. Anyway, here it is, the problem I think is that it makes the top of his head look a bit bubbly, I’ll fiddle with it more (hopefully get gimp to work properly too) and it should be hidden anyway once I add hair.
I suspect it might look a bit rubbery because it doesn’t have a specular map yet (only a specular ramp shader at the moment), that is on my todo list 
