I can tell that it's him, which is pretty tough to achieve! I like most of the proportions of the face. There are a few things I would tweak.
There is a sharpness at the glabella that might need to be softened.
Cumberbatch has such an awesome brow ridge, in most pictures I see of him there is a deeper deviation at the temporal bone (behind the zygomatic arch.) Whether this is from an extruded occipitofrontalis or a deeper temporal I'm not sure, but you may want to try playing with that ridge.
I would also work on the hair. How his hair covers his huge dome makes or breaks Cumberbatches likeness. Great start!
Small update, cleared up the glabella and made some tweaks to define the brow ridge more as you pointed out nGreenroad. Pushed back the temple a bit and compressed the face vertically a bit (felt it was just a bit too elongated). Defined the base for the hair and scarf but I'm gonna go back to the face for a bit, I'm not quite happy with the zygomatic and I figure it's better to get it perfect before introducing asymmetry.
Replies
There is a sharpness at the glabella that might need to be softened.
Cumberbatch has such an awesome brow ridge, in most pictures I see of him there is a deeper deviation at the temporal bone (behind the zygomatic arch.) Whether this is from an extruded occipitofrontalis or a deeper temporal I'm not sure, but you may want to try playing with that ridge.
I would also work on the hair. How his hair covers his huge dome makes or breaks Cumberbatches likeness. Great start!