Quick answer why it’s unbearable to use online version – PostgreSQL manual consists of the 1036 topics and I don’t like search engine on the site at all. It is also worth noting that the tree of contents in CHM version speeds up navigation a lot!
Good friend of mine, colleague, passionate fan of Perl Edward Smirnov obsessed with creating a utility capable to compile the help in CHM format using a set of HTML / SGML files shipped with PostgreSQL. He managed this! The only thing missing is the Index (HHK file in CHM archive) support.
However, even without this feature such manual a hundred times more comfortable for me than the online counterpart. Especially I’m excited about lightning full-text searches.