Working screen > bad screen, but original screen > modern screen.
If there was a laptop I really loved for the form factor, and my only option for using it was a modern reproduction screen, I'd take it. But the original screen's appearance/quality is a huge part of the appeal for me - be it passive matrix or active.
If you can find a panel in the right size and resolution, and work out how to interface it, I think it's a great idea. Though I suspect that could be a big "if" unless you're willing to hack up the bezel to accommodate a display of a different size and aspect ratio - a lot of the mono PowerBooks whose displays suffer the most are 16:10 640x400, which is a bit of an oddball.