Wow! amazing!
I agree with Skurwy about the highlight, but I'm not sure dithering would be ok, this is a shiny surface. I'd say add 2 more light tones and have some AA.
if only the color was there (and you have a nice field for experimentation), id say it was taken alive from chaos engine. im really in awe watching how meticulously you have rendered the curves (although its pretty small after all). the only thing that bothers me is the complete lack of dithering over the sphere surface -- where the light hits it. looks too sharp as to my liking. please do something bigger now!
Great avatar!