So far so good, saved me probably $100 or so
Worked like a charm.  A bit tricky to unfasten the assembly from the overall tube cover of the toothbrush, but once out I simply unscrewed the broken shaft, screwed in the new one, snipped the old copper wire and twisted the new one so I didn't have to solder.  Taped down the wire around the twist to ensure it stayed in place and now the toothbrush works great.
Rating: 5 stars