I feel like this is an unfair criticism. We all have pdf readers.

Lack of linux support is only a worthy criticism because appearently portability is a primary design goal and this is going to "replace" linux, but in general that's criticizing the tress for lack of seeing the forest.

PDF prints well, and has nice search features, and has a nice zoom feature to accommodate people of different visual acuities, which the web does not always do well. This is the first time i have ever seen anyone prefer the web. Maybe if i put a table of contents in the PDF that would help.

There are some people reporting that the Windows .EXE runs okay under Wine in Linux, but yes it would be nice to support Linux desktop natively.

I share your surprise: are there any major languages with a PDF as their main documentation source? Nothing beats an hypertext at looking for something IMHO.