Charlie,
Foredom was always considered the best of the motor tools. The only problem I've had with flexible shafts is that they (the shafts, not the motors) tend to get very hot if operated with a sharp (90 degree) bend while working. I try to position the motor head so that the shaft is as close to straight as possible. I think they are supposed to be disassembled and lubed regularly.
Is their lubricant graphite based? I've been using a powdered graphite that I think I read somewhere was good. But maybe not considering the heating problem!
Jim