The /System and /Library folders were invisible from the beginning of MacOS X.
The ~/Library folder was not. And several applications stick things in there that users are expected to edit manually in order for the application to work. X-Assist for example creates its menus based on the contents inserted manually by the user in ~/Library/Favorites/X-Assist Items.
OK, it (X-Assist) hasn’t been updated in awhile. So? The decision to make ~/Library freaking invisible is a change in OS X behavior. There should be less hidden ways to change that.
(There should also, of course, be ways to restore the ^#$@!@#& scrollbar arrows in scroll bars. I’d pay $100 in shareware fee for a hack that would put the damn things back especially for horizontal scrolling… but I digress)