Which Powerbook?
I don't find my DLSD keyboard very different from the one on my early '08 MBP. It's quite different from the "chiclet" keyboard of the unibody MBPs. I find it a lot "softer" but with a little bit more key travel. I also prefer the key shape, which is depressed(with the key touching each other) unlike the flat keys on the chiclet boards.
The TiBook keyboard has a somewhat similar keyshape to the AlBook keys. The travel is probably a bit longer than the AlBook, and it's also fairly "crisp."
Of the three, I prefer the Ti, but have spent a lot of time typing on all three and can type really well on the Al/early MBP keyboard. I probably have the most typing time in the chiclet board, though.
My 12" PowerBook has a very good keyboard. There's a lot of tacticle feedback and decent travel.
My 15" DLSD from the same year had a very mushy keyboard in comparison. It felt very awkward to type on it and I didn't like it at all. I don't know if that's normal on those or if I had a bad one. @bunnspecial has it now, so maybe he can say whether that's normal or not.
Now *there's* a machine that I used to want back in the day.
I forget, did it run CP/M or Valdocs?