Yeah, it can show screensavers. Cool Mac OS X screensavers like Flurry that beat the pants off typical Windows ones.
The speakers are right above the keyboard (check some pics, you'll see what I mean). They're on the same horizontal plane that the keyboard is on, but pointing towards you (they point in the same direction that the keys point in). Sorry, I can't think of a better way to describe it.
Nope, the PowerBook is the laptopo supremo, sorry. But the iBook is a great consumer-level product. It's cheap, very powerful (although not as powerful as the PowerBook), offers plenty of expansion options, and now offers built-in wi-fi. And it looks good.
If you're just doing web surfing, email, word processing and the occasional game, the iBook offers the best bang for your buck. It's actually quite powerful, great battery life, etc. But unfortunately the PowerBook is better. But it's also almost twice as expensive for comparable models. But you do get what you pay for.
Good luck, hope this helps,
m1k