I have the 12" iBook 1Ghz model with 512mb RAM and AE (otherwise stock standard).
I chose it because I needed a laptop that was light as possible because I have to carry it to/from and around uni a lot. Yes there are laptops lighter than the iBook, but I had a budget of $AU2000 and I wanted my optical drive and HDD to be internal (which is how some of the ultralight laptops manage to keep down their weight).
So with my budget and wanting something light, I found there is about two choices that I had - an iBook, or a Dell. So I pretty much decided on the iBook right away - better built, i liked the colour much better than black, it runs OSX (while I didn't have problems with viruses on my old laptop, I did have problems with Windows), not only did I get education discount on it but Apple gives 3 year warranty for free to students in Australia (not quite as comprehensive as Applecare but still), plus it came with a lot of useful software included (iLife etc).
I have been extremely happy with it (no major problems, and I'm surviving quite well in an IT degree that wants you to think you MUST use Windows). I'm especially happy coming from my previous 6 years old IBM laptop - it weighed 3KGs, 12 in screen, had CD ONLY drive, a "whopping" 128MB of RAM (64MB soldered, 64MB in spare slot, max it can take is 128MB in spare slot), 6GB (5.5 true/usable gigabytes) HDD, 466MHz Celeron, an "impressive" 4MB graphics card, trying to run Windows XP (a lot of applications I used for uni needed to be run under XP).
Edit: just wanted to say I get about 4 1/2 to 5 hours battery life WITH Airport ON and screen under 1/2 brightness, which extends up to 6 hours if I turn Airport OFF. This is with web browser, several chat programs, mail, iCal, a note taking program (when I'm in a class) running. I've also managed about 3 to 3 1/2 hour battery life when importing and editing a video in iMovie for my brother's assignment.