well, an extra 100MHz is always nice, but ill be a bit dismayed if apple sticks with 128MB of RAM in the lower two models...
obviously OSX will run on 128MB, but have you tried it?
when these machines are clearly aimed at newbies and students as well as existing mac users (who know about these things), wont they feel like they are using ancient slow monsters running OSX on 128MB RAM?
if you talk to people who dont have much of a history with computers they expect them to adhere to the same rules as any other expensive purchase like a HiFi or a TV - they wont realize that they just bought something that needs upgrading right away. its this sort of pan-handling that gives technology in general a bad name...
also, isnt IBM making 1GHz+ G3s these days? you would have thought that if the G3 days are numbered in iBooks, that apple may as well use the best they can get...
...then again 'upgrading' the 1.2GHz G3 iBook to an 800MHz G4 when the time comes might not look so good