Instant Expert: Secrets & Features of iTunes 8.2 is quite thorough. Good stuff about iPhone 3.0 compatability.
Kirk McElhearn says in iTunes 8.1 and Large Libraries: More Progress on the Speed Front that the speed is there.
My good friend Kirk McElhearn has an article up at Macworld on syncing multiple iPods to one Mac:
When you're alone with your iPod and your Mac, it's easy to manage your library and sync your music, videos, audiobooks and data. But with the holidays over, many family members who didn't have iPods beforehand may now find themselves the proud owners of one of Apple's music players. And when two or more people share a Mac, it gets a bit confusing. There are several ways you can sync multiple iPods to one Mac, but the easiest method is to share a music folder. Here's how you can share your music with another user on your Mac.
I've just posted a brief article explaining how your system can get confused when using iTunes' multiple library feature:
Some of my AppleScripts for iTunes use a routine which reads the iApps.plist in order to obtain the location of the current iTunes library's XML file in order to get information from it. I occasionally get reports that these scripts don't seem to be working correctly; that the information seems to be wrong or doesn't correlate with track tags in iTunes. When the Correspondent and I investigate this phenomenon, very often it is because the iApps.plist contains the wrong location for the current iTunes library....read more here.
This tip at Mac OS X Hints reveals the defaults command to keep track numbers from being added to the beginning of filenames after importing, a feature that was removed from iTunes' Preferences in iTunes 8. Of course, as one commenter laments, this won't remove the track numbers from files you have already ripped in iTunes 8.
iLounge has an excellent overview of the new features in iTunes 8. Particularly good details on the Genius features.
Switch off the iTunes 8 Genre browser via a defaults write command in Terminal.
Something I had not known until reading about it in the X4U mailing list: apparently, Time Machine does not back up the "iTunes Music Library.xml" file. This is the file that is periodically updated by iTunes which contains track and playlist data. It isn't used by iTunes, but it can be used to re-import data and what not. Most of the time, this file is located in your [username]/Music/iTunes/ folder (you should not relocate it). Thus, if you are concerned about this file, you may have to manually back it up, independent of Time Machine.
UPDATE: A post at Mac OS X Hints discusses what files are ignored by Time Machine and how to list them.
UPDATE ALSO: Any copy of the "iTunes Music Library.xml" file that is not [username]/Music/iTunes/Tunes Music Library.xml will get backed up. So periodically copying it as something like [username]/Music/iTunes/bu/Tunes Music Library.xml will ensure Time Machine sees it.
My friend Kirk McElhearn has a very fine article at Macworld on working with album artwork: where to get it, how to get it, and so on. He mentions that the CD Universe website is a good place to snag album artwork and so I thought I'd slap together a quick script to search the site. Search CD Universe for Album will use the album tag of the selected iTunes track as the basis for a "Title" search at CD Universe. You'll have to manually navigate the site once the search results page comes up, but at least the script gets you started.