I thought you'd link to this, which is better:
http://www.franz.com/support/documentation/8.1/doc/contents....
...which I'd say is probably the best of the online manuals.
But more to the point:
There are minor issues with the formatting of the hyperspec no one's bothered fixing. Aside from the lack of a pretty stylesheet and the lack of wiki-style user comments
The most obvious is that if I eg go to the Strings or Array section it just gives me a page with a sub-table of contents; it'd be a lot friendlier to have all the Array or String docs on a single html page.
This wouldn't even be that hard to implement, and the "moar docs on one page" approach to online docs keeps winning out for a reason (it's easier to find what you're looking for if you only know approximately where it is if you can get everything that might be related on a single page and ctrl-f your way through it; having deeply-nested content is far unfriendlier).
I do think the hyperspec is not very well-thought-through as end-user documentation.
It mixes levels of concerns that ought to be separate; someone reading documentation with the goal of finding out if there's a built-in function for "split a string delimited by a particular character into a list of strings?" has very different requirements from someone who needs to know how strings are implemented, for example.
IMHO the hyperspec tries to do both; it's fine as a nitty-gritty reference but could be improved as a day-to-day programmer's reference.
Python's docs are a good example of end-user documentation done right. They have a clearly-delineated split between the language specification ( http://docs.python.org/reference/index.html ) and the standard library specification ( http://docs.python.org/library/index.html ) and additional, separate documentation over lower-level aspects of implementation.
Each body of documentation is organized for the convenience of its typical user.