From the first work you posted up to now, i've had the same feeling on each of the pieces: that you pixelled it then added a grey layer at 25 to 50% percent tranparency on top. I partially agree with adarias, though i believe that you should increase the contrast, rather than saturation, between your colors. I think the key to maintaining the (relative) realism you're striving for is to choose which colors to maintain low-saturation and low contrast, and which ones to increase these factors.
In the third and fourth pieces you posted, i've seen you move towards this goal, but you still have a bit more to go.
Regarding the hue shifts, they look good on the skin, but on the first one's shirt, the pinks/oranges look out of place. Generally speaking, i think pinks/oranges on hue-shifted areas that are mainly composed of white/gray, look like noise. Yellows are okay though. Adaria's edit has fixed this apparently.
On the anatomy, i suggest trying to do slimmer figures, with less muscle volume, to achive easier silhouette reading. The anatomy on your figures, while looking good, seems to have the muscles stopping free movement of the limbs (back muscles attaching the torso to the arms via the biceps, legs touching each other because of the thigh muscles).
Edit: oh, and another thing: in my eyes, eavily hue-shifted pieces look great at 1x zoom, but not so much 2x or larger. The more radical hue-shifts just look out of place (not you work specifically, speaking generally).