It took them quite a while, but today my iBook is back! Finally. I was at work and the NextByte service guy called my mobile, saying that my iBook is ready to be picked up. It suffered from that dreadful logic board problem which plaqued many G3-based iBooks, and they have to replace its logic board. So I quickly went down to the NextByte, which is only around 5 minutes walk from my work place, and picked up my iBook. I did some testing after bringing it back to the office. Everything seems to be working, and no file is lost. I'm glad that it's working again!
NextByte has a nice job report, detailing who, when and what has been done to this particular job. Interestingly, the actual logic board replacement only took one single day (happened 3 days ago), and the rest of the time my iBook probably just sit on the shelf waiting to be attended, or waiting for the new logic board to arrive. Still, with a detailed job report like this, it is still much better than "nothing" presented by AppleCentre at Taylor Square, where I had mine serviced last time.
And finally the verdict is, especially with notebooks it is worthwhile to buy extra warranty, in this case the AppleCare. It is a bit like buying insurance - some people might never need that extra protection. The Dell that I used for work lasts 3 1/2 years and is still going strong. But just in case you do need the problem fixed, a logic board replacement would cost more than AppleCare itself.