He's very popular, written several books and spoken at many events. Most notably he's written Clean Code and the follow up I never bothered reading and he's a die hard advocate of TDD and also one of the authors of the Agile Manifesto. I met him a few times after his talks.

I generally "like" Uncle Bob or Robert C Martin insofar as he advocated for better software design and had some good ideas and all that. I personally hate TDD but when you talk to him and stuff, he's more flexible and nuanced than he can come across. The problem is when he comes up with (or runs into) a new "philosophy" he becomes evangelical about it and it seems like he doesn't have as much nuance. Sadly though, growing up with his fans in the software industry has been a pain because they'd hear something from him or Fowler or Beck or whoever and then try to reshape the codebase like typical Magpie Developers.