Stuart,
You're right to keep your hopes up. I had a table-saw accident during my high school years. Didn't cut my finger off, but opened it up linearly, for lack of a better term.
In essence, the tip-bone of my left index finger is supposed to be sort of arrow shaped - well half it is gone. The fingernail is a mess, but there for protection. Surgeon spent a good 4 hours working on it. There's even a skin graft on the back side. I am not supposed to be able to straighten that joint once I bend it - it works just fine. The entire finger tip is supposed to be numb - it's about the most sensitive part of my hand - I use it to decide if I'm really done sanding. And it's been working well for the last 30+ years.
So, chin up, and best wishes!