I'm typing this entry on my shiny new iBook. I got it Friday morning, but this is the first real chance I've had to play with it. I've not really found much out yet. I had a slightly worrying moment Friday night when I was populating the hard drive with the restore CDs (not sure why they can't ship the hard drive with the system set up on it). It complained that the modem couldn't hear a dialtone, but seemed to connect to Apple and submit my registration and iTools details fine. However, when I started trying out apps, the modem claimed to still be connected, even though it wasn't (I could hear a dial tone on the line via my phone). Disconnecting just hung. Anyway, I tried again this morning and it seems to work fine (I'm using it now to SSH into the lab and type this), so it's probably just a glitch in the installer.
The only other problem I've seen so far is the on switch. It works fine, in that it turns the computer on and off, but I swear I saw the switches on other iBooks glowing (similar to the collar on the power connector). I'll check this out.