It depends on what you are used to and which web pages you visit.
For reading blog pages or text news pages it's absolutely fine.
If however you're used to a 20" desktop display where you regularely place 2 web pages side by side - e.g. to compare tech specs pages - the 12" screen will seem painful.
Speaking of pain, posting to this news group is a bit of a pain too if you intend to use the 'Preview Reply' feature or vB Code buttons.
With your post in a preview at the top and the message entry field below the 768 pixel vertical resolution is not enough to display your preview, the message window and the 'Preview Reply' button at the same time, not even the vB Code buttons. You end up scrolling up & down & up & down & up...
But as was said above, the size of the PowerBook is fantastic. Very mobile. If you are the type of person who likes to sit in WiFi cafes and surf the web, the 12" PowerBook is the way to go.
I just wish Apple would have a BTO option for a higher resolution 12" display. That would be nice.
Apart from that you'd probably have to go with a 17" PowerBook to feel any noticeable difference on the vertical resolution.