I was lucky enough to be shown carbon fiber fabrication by Craig Calfee, and used the material for awhile to fabricate recumbent racing frames. Easy to use, relatively inert in the various formats available (in many ways what carbon picks up from the fabricator or tools, namely oils, is worse for it than direct contact is for the fabricator) and used in conjunction with epoxy resins (much less noxious than esthers), carbon can be a pleasure to work with. When sanded or cut, it is another thing.
The particles are very small and invasive, cause terrible itching and possible rash, potential respiratory irritation and worse. I am encouraged by any attempt to re-use or recycle the material, but really think that the world doesn't need to be using the stuff, and that is why I no longer do.
As for repairs, done correctly they work well. Never as elegant as the original, but nonetheless dependable and trustworthy. I, too, think that nothing works as well, for all effected, as steel. Truth seems to be that if we were a tad more creative/resourceful and a lot less acquisitive of shiny, new objects, then we could never make another new bike and be just fine....keep using, repairing, customizing and reconfiguring what exists.
As for the potential danger from handling a damaged frame, I would say just don't inject the frame into your abdominal cavity and you will probably be fine :) Touching the stuff, especially any form other than dust, is not an issue.