First of all--I love this picture! LOL It's creepy, and fun, and weird, and pretty realistic. Definitely an interesting concept.

A few things that I noticed: the ring and pinkie fingers...hands?...the hands on the pinkie and ring fingers are twisted so that they don't match the natural twist of the fingers. Those two fingers sort of turn out; it seems the hands should turn outward, also.

On those two hand/fingers, and also the middle and a bit on the ring, the seam between finger and hand is obvious...it's mostly the hair. The hair starts and stops a bit abruptly, and I think if you could have chosen a non-hairy hand, or perhaps edited out the hair, they would merge much more easily with the fingers.

The middle finger-hand seems a bit small for how big the finger is. Comparing to the other fingers, the hand/finger size ratio is a bit small.

The last thing is more a suggestion than a correction: perhaps the thumb/hand could be a right, rather than a left hand? It seems a right hand might fit the opposing thumb a bit better than the left hand...sort of to balance out the left-hand fingers. (Critiquing a hand full of hands can get confusing! )

What I like: I love the transition on the thumb and forefinger. Except for the hair on the forefinger, they look flawless to me, and the shadows and lighting seem to match up fairly well. The knuckle lines on the thumb, in particular, really go well with the wrist/lines of the hand.

I love the concept in general. As I said before, it's interesting and a bit creepy--I'd love to see a hand like this in real life. You've done a good job matching up the colors, too (assuming they're all the same hand?). The overlying texture is nice, too.

Good job! : )