Hasn't changed much, I don't think. from the beginning, yeah, there has been great improvement, but I think that the recent changes have been very small jumps. Not that it's a bad thing, but it certainly wouldn't hurt to be a bit more adventurous, man.
I made a small edit (just the head). I'm really not as good as some of the other people around here, but I think that it still shows some possible improvements.
One of the things I didn't like was that the light source seemed to come directly from the side. It's probably a personal thing, but I tend to find that to be a bit boring (and unnatural, at least if he's outside). I shifted it up a bit more but kept it going in the same general direction.
I added more depth to your palette by upping the contrast significantly (it's actually a whole different palette, sorry). It could still be improved, but it was a quick job. I also tried to give the head more form to it, by making a shape out of the brow area and stuff. It seems very blobby as-is.
Another problem I had was that I didn't really know what was going on with the mouth area. Are those things tusks or what?