Yatzee will soo bash Portal 2, there is no way in hell that he will not find tons of stuff to pick on.
Here's a list of things i think will definately be mentioned:
-Due to incresed lenght and complexity he will b*tch about it getting too difficult, boring or repetitive.
-The humor will not compare to that of the first one, unless they bring back the cake meme (ok, ok this part has nothing to do with yatzee, i just thought it was fun so I added this line, of course the cake would be one of the first things he'd pick on ).
-The fact that the same caracter is used despite the fact that more than a hundred years have passed.
-Random other not-really-important game aspects like how some wall tile is a little more color saturated than another or how Chell's leg bracers make her look like a victim from the movie SAW.
Oh and he will probably be dissapointed about the still nonincandescent-titless portal gun
However these are just my thoughs on the matter, what do you think ?