How much do you tether? And to what sort of devices?

The problem I have with T-Mobile is their customer service reps are so poorly trained.

So depending on who I speak with, I am told I either need to pay the $15 for tethering or not. I pay it as I am a bit afraid to drop it never to have it return.

So can you tell me more about how you much you tether, and how often? Or if T-Mobile has ever given you anything official about your tethering being okay?