A few technical critiques : the palm is rather flat, the middle section of each finger is too thin, and I suspect you’ll save yourself a lot of trouble later on if you leave the fine wrinkles & creases (like those on the knuckles) to bump mapping. And I agree w/ dshelton about the nails. It should look like they’re growing out of the nail, not sitting on top. It looks like you model your nails the same way I do - with two bevels? - so I think if you just play with the vertices of the nails themselves that should be a quick & easy fix.
Also, if this hand is going to be the focal point of your whole image, I suggest making the anatomy uber-defined, like something you might expect to see on a greek/roman sculpture. Or soft, pudgy and child-like, if you want to go that light-hearted route. Either way I think the structure/modelling of the hand itself should be enough to hold the viewer’s attention.
That’s a pretty good looking skin texture, btw.
