"A worn driveshaft bearing will generate strange vibrations that you will be able to feel in the cockpit, and may also increase the amount of "gear noise" you hear while driving."
Presumably, if your driveshaft bearing is shot, either:
1) the driveshaft is having a hard time rotating (gearbox sees this as extra load).
2) it is rotating freely but having a hard time getting power through that joint (gearbox sees this as no load).
Both might cause vibration and hesitation... the hesitation part is a bit scary... get it fixed.