They really do get quite warm, especially while charging the battery.
They wear out on occasion, and I like to have a spare on hand in case that happens. If you are concerned about your adapter, you may want to buy another in case that happens. I've worn out four adapters. It's also nice to have an extra for troubleshooting situations.
Upon doing a lot of searching, I have found the following options for replacing a white iBook power adapter:
http://www.macresq.com/store/detail.php?prodID=P009141
MCE Technologies
http://www.madsonline.com/index.html
http://eshop.macsales.com/Catalog_Item.cfm?ID=6432&Item=MICACADPTG4
MacAlly adapter at Buy.com
Apple's is the only one with the glowing ring, though, and is found here:
http://store.apple.com/1-800-MY-APPLE/WebObjects/AppleStore?productLearnMore=M89 43LL/A
I believe the one from Other World Computing is the sturdiest of the lot. We've tried most of them. The one from MacResQ gave out after two years. The MacAlly one has a thinner cord, and it looks more fragile.