I really enjoy his blog posts and his work on automata seems to be well respected. I've felt he presents a solid epistemology.
Furthermore he has a very long history of grossly misrepresenting his accomplishments, whether by claiming authorship of his employees’ accomplishments or denying he was ever exposed to work that he built upon.
For example, I believe it’s been proven now that he had substantial exposure to MACSYMA before he started to lead his employees in the development of Mathematica—but that didn’t stop him from claiming it was entirely original and even threatening others with patent and other IP infringement claims for trying to do things that were similar.
(Which is the other problem with him: He doesn’t just take credit for the work he pays others to do, he’s an “IP protection” maximalist.)