Greg Beaver points out today that the sample chapter [pdf] of the "PEAR Installer Manifesto" has been posted by Packt Publishing.
Packt has put up a sample chapter, Chapter 5 "PEAR Channels: releasing to the world" up at http://www.packtpub.com/files/SampleChapter-The-PEAR-Installer-Manifesto.pdf. Check it out to see what you're missing if you don't already own the book.
The chapter he points to talks about setting up a channel (using Chiara_PEAR_Server) and why they're the "killer features in PEAR 1.4.x+".
You can get the full information on the book from its page on the Packt Publishing website and order it directly or from another retailer.