But not every use. I routinely us a Compact Flash Card adapter to transfer images from the card in my digital camera to my Powerbook. This is a lot faster than using a USB cable or reader and a lot easier than dealing with the cables of a FireWire device. Similar to the PC Card is the expansion bay. Whichever one I use does need any cables and is not another thing to carry around town with me.
General performance is another issue.
With a 500MHz Powerbook they used to test, the iBook provided slower performance. Now realistically speaking these aren't massive performance difference. In real-world scenarios, I'm guessing they aren't even noticeable. That just means that a 2001 iBook offers pretty much the same performance as a 2000 FireWire Powerbook. It isn't a reason not to buy a new iBook at all, but it does point out that you won't gain any performance going from a FireWire Powerbook to a 2001 iBook.