About Ken Rockwell, I've heard him described as a "black and white photographer shooting in color" - he likes contrast & texture, and generally shoots stuff that would look better in b&w.
What do you mean? The site is free to browse and what little ads there are, are unobtrusive.
Content-wise, I personally find his take of not spending time pixel-peeping refreshing, but to each their own, I guess.
Ken passed his technical prime and photographic abilities many years ago. That website is mostly bad information and should be wiped from the internet archive.
I think his site is a great resource if you want to look up older Nikon glass. About the new stuff (mirrorless, etc) ... I don't know ... take it with a grain of salt.