[AnimalMuppet]

I have seen plenty... but not all that much substance. Much of it had the form of "How could they be so stupid to make those design choices!", as if the author's preferred approach was The Only Right Way. I've seen criticism that said "They couldn't have known anything about Modula 3 for them to make that choice!", when in fact Rob Pike talked about stealing an aspect of the object file format from Modula 3. Yeah, he knew it, and probably knew it in more detail than the critic did.

Apart from "They should have done it the way I like!", the main criticism I have seen is lack of generics. That's a pretty common complaint, from a lot of different people.