I trust, and use the autopilots in the later 172's (R and SP). It's a real
work-saver, and as such contributes to the safety and comfort of the flight.
The recent 182's have the same setup. You can do some basic tests before
takeoff, to make sure it's doing more or less what it's supposed to.

I recently rented an older 172, with a Nav-o-Matic relic. I've never flown
with one of those things, so I left it alone. For all I know, it's just as
reliable.

G Faris