Lets be clear, no iBook is going to give blistering performance, if you want Facebook or a modern browsing experience look elsewhere.
My iBook is fantastic for carrying around and writing, the battery life is great and keyboard is pretty good as well. Plus it supports WPA2, which my old Pismo doesn't. Parts aren't to expensive to come by and the iBook isn't THAT hard to service unlike some other Apple machines.
Like many on here, I like using old macs and not discarding them simply because they can't handle the bloat that is now the internet. I actually like the fact that facebook is a no go, because it means I have no excuse for not getting on with my work. When you have writers block you'll do anything to avoid actually writing, which only makes things worse.
So yeah, sitting in a coffee shop with my bluetooth headphones on, listening to music off my iBook while getting on with work ain't so bad
If you want a distraction free device, which you can use for writing, coding, art, then an iBook will fit the bill. I only started using a G4 15" Powerbook because I needed the bigger screen for design work.