I don't want to get into the middle of a huge flame war, but I wanted to say that I think Apple did an awesome job with the split-disk install of Leopard that I'm working with right now. I've had to install operating systems a number of times, and installed software all over the place, and one of the things I've noticed is an inconsistency in checking to make sure you have all the disks. I just got done walking through the wizard for installing a fresh copy of Leopard, and the last thing that I was asked was if I had the Mac OS X Install Disc 2 handy, since I would probably need it. The nice thing about this was that it was done just before the format, so it was the last little check, just to make SURE that you were ready to wipe things out.
Once more, not trying to incite a flame war, but I found this MUCH more comforting than when I tried to install Windows Media Center 2005 back a few years ago and only realized that I was missing a disk when halfway through installing files, I was told to insert Disc 2. It was my own fault for not checking before I started, but we don't reinstall every day, so it is nice to have little reminders, sometimes.
I don't remember when it was that I first saw it in Linux, but I do remember on Red Hat or Fedora, being given a list of the CDs that I would need to install the packages I had chosen. I remember at the time lamenting the fact that I couldn't install a base system off of one CD (which, as far as I know, is still the case if you don't download the DVD). Now, I use Ubuntu for all my Linux-licious needs, so one CD is all that I need and all that I want.
P.S. If you didn't know, you can install a small jailed copy of Ubuntu Desktop 8.04 on an existing NTFS partition. I just installed it on my co-worker's Server 2008 box for him to find in the morning. With getting the OS installed and dual monitors working and ready for a reboot back into Server 2008, I invested about 10 minutes in the prank. That's some nifty software!