I think that the PowerBook 12 inch will go down in history as one of Apple's best laptop Macs.
A few years ago I got my Dad one. About a month ago, I asked him if it was still working okay. He said that it's working just fine. I mentioned that I was thinking of getting him a new MBP13 ... he sounded hurt.
Anyhow, I did make him promise that I get it when he upgrades if that ever happens.
The last time I visited Akihabara, I saw a store that had a bunch of them for sale. Expensive! They have sure held their value over time.
Now with the MBP13, I don't think that we'll ever see something like the PB12.