Interesting rig. Here are some observations. I realize it's still Wip but you said you wanted feedback so here goes.

The neck looks fine to me but the head bends have alot of sharp distortion. The collars need to be used sparingly to avoid what I would call soft distortion. This is true for most poser figures so I think yours are better than most.

Shoulders, Arms and ForeArms can cause sharp distortion when using Rot-X. Rot-Z has some problems as well but not as much as Rot-x. Rot-X and Z do need work but if you use each part sparingly it's not really as much of a problem. Rot-X from Shoulders to hands is the weakest part of the rig IMO.

Rot-Y has possibly some of the best bends I have ever seen. Being able to move the arms straight in front of the figure without it collapsing/distorting the chest/deltoid/Lat areas is something just about every figure has big trouble with but you rig does it really well.
It aint perfect but it's really really well done. The best part of the rig IMO or atleast close to how good the 2nd hip bends.

The Chest,Abdomen and hip all look fine to me.

The 2nd hip could take some getting used to but it is impressive and powerful for natural movement and posing. It's quite interesting that the hip and upper thighs are one group. I know nothing about rigging but I can see that is the main reason it bends so well in that area. I could be totally wrong but it just seems to me that's the reason it bends so well there ( that and JP's of coarse ).

The legs
With IK on, the heel moving with the legs when twisting the leg/shin is a bit odd. Fine for stills realistic I suppose but not so great for animation.

I only checked out the higher-res one so far. Over all it's an impressive rig that has a lot of potential over other figures if posed right. He can look bad if not posed right but alot of figures can look bad even when posed at thier best in the more difficult for poser positions.