I have no doubt these custom voices for your TomTom or Garmin GPS cease to be entertaining after, oh, about three blocks, but if you’ve got money to burn, go for it.
Most are groaningly bad, but they have their functions:
GlaDOS: good litmus test for whether people you’re with are huge nerds.
Pimp or sexy lady voice: good test for whether you’re a raging misogynist (or closet prostitute).
Yoda: Eh, why not?
If you’re curious but poor (or care to exercise good taste, like me), you can listen to samples, so at the very least you can laugh at W saying “arrived at destantination. Mission accomplished,” which is funny even though the Bush imitator is only passable.