I wouldn't like the idea of Yoda being changed in TPM, and I would have to lead an angry mob to Skywalker Ranch if Lucas ever even thought of replacing the puppet in Empire. Even though the prequels suck, Lucas changing any of his movies is a bad idea just on principle. If we happily accept changes to the prequels, then it makes us look wishy-washy when we complain about him changing the original trilogy.

Besides, even though Phantom Menace Yoda looked way too young and kinda Muppet-ish as well, he still had those eyes. Those classic, Stuart Freeborn, YODA eyes that define Yoda so well. The CGI Yoda's biggest flaw is in the face and the inability to recreate those Yoda eyes.