In my opinion, the worst thing to happen to the alien design was the change from 4 fingers and two thumbs to just four huge fingers. The six-digit idea was much cooler and I liked that interpretation of how the alien would take human characteristics and kind of enhance them. A four-fingered beast just seems cheap.
Aside from that I was a fan of the AR aliens. I used to like the ridged skull back in the day but now I prefer the smooth dome. My beef with the new design is the mouth. It looks like when you make a duck shadow puppet and open and close your hand to make its mouth do the same. There is no cheek or lip definition... just a lever opening up.
Oh well.