This may be of interest. Or not. YMMV.
Listed below are a pair of links to webpages -- at opposite ends of the same spectrum -- which give a handy guide to what's new! and improved! in Mac OS X 10.4 "Tiger"...
A very long, detailed, comprehensive review, including philosophical ramblings and opinions, from Ars Technica: http://arstechnica.com/reviews/os/macosx-10.4.ars.
Apple's own list of the "200+ New Features", with synopses, listed by category: http://www.apple.com/macosx/newfeatures/over200.html.