He may know a thing or two about language implementations, but his complaints are predictable: he wants it to look more like perl and less like Java. Additionally, his opinions on the implications of their concurrency model are entirely based on perl's implementation and IMO not necessarily correct in another context (message passing was probably chosen specifically to avoid needing heavyweight threads). I'm not a web programmer but those complaints seem superficial to me, I'd probably spend a little time using it before coming to that conclusion.