The PowerBook I'm currently using was through an Apple-company-discount refurb program and OH, HAS IT SUCKED.
It's the only Mac I've had which has tested the "Windows feed on hate, Macs run on love" theory which has been my mantra since owning my first Mac SE/30 in college. This 17" PowerBook G4 showed up loose in the box, meaning no packing materials during shipping, it had the wrong restore discs packed in and, the piece de resistance, the outlet-to-adapter cable was missing.
Because it was not packed right during shipping, the PB had probably been damaged before it ever arrived. It experienced a range of problems which required it to be taken back to the Apple store a number of times. If I'd properly documented the problems, I probably could have negotiated for a new replacement. But looking back, I should have refused receipt of the computer the moment it arrived. What a trainwreck. But as trainwrecks go, it's still running four (five?) years later. Kinda.
My point is (and I do have one) if you get a refurb and it is IN ANY WAY discernibly different from a new item, refuse it and ask for another. Seriously.