Even with the very modest hardware of the Comma 2, it effectively takes all the stress out of highway / stay-in-lane driving. In my Audi A3, the car's ACC handles the accelerator and brakes, and openpilot handles the steering. It made the trip a whole lot more relaxing. It was also just a whole lot of fun to set up and tinker with, the community is great!
I haven't been able to observe anything close to the same quality of assistance system in any other car. Autopilot in a Model Y I drove just a few weeks ago felt plain erratic compared to openpilot, and the way it disengages completely when you make even just a small correction is really annoying. Audi's latest assistance systems silently give up as soon as the lane lines aren't 100% clear or things get a little too curvy.
If they can effectively make use of the additional camera data the Comma 3 offers in future openpilot releases, this will be well worth the price tag.