My MinnKota TM was donated to me by another crappie.commer but it just happened to have AutoPilot which I didn't know anything about. I read up on it and started using it. Now I don't think I could use the TM without it. My understanding is it uses compass heading to keep course. Seems to work pretty well for the most part. I like the fact that I can set it and forget it (haha) while I'm rigging a pole or landing a fish. I know the TM will be doing as much as it can to keep me going in the right direction. It does take some getting used to. And I think it works much better at medium to high speed, especially if there is wind pushing the boat. It can't really compensate enough at the lower speeds. All in all, I say it's Good. You can always turn it off if you don't like it.
Just some added info from the Minn Kota site. Click here.