I am not happy with them: recently I was looking for the API docs of the standard library for Ruby 1.9, and it turns out it is not available online anywhere. ruby-doc only has the 1.8 stuff. I spent hours trying to figure out how to create my own documentation with rdoc ad ri but eventually gave up. So now I don't even have the documentation of the standard library for Ruby.

Plus you can do a custom Google search like this:

      http://ruby-doc.org/q/<your search string>

ruby-doc.org is nice, but there's a lot missing in the package level (FeedTools etc). Also, it could use a lot more code examples.

Here again I think it's interesting to compare to PHP's annotated docs ca. 2000, which were a great resource since they usually contained a few common usage examples for every function. The language itself was less consistent and mature than Ruby, but the user contributed (pre-Web 2.0! ;)) docs made up for it.