My surgeon let me drive at six weeks, which I think is pretty standard for him. (My cardio's nurse practitioner thinks OHS patients should wait EIGHT weeks. I would have gone quite mad if I had had to wait that long.)
I don't recall having any problems driving ... although I was told I might feel some soreness (arms, shoulders, neck, sternum) but I actually did not. But then, I had very little sternum pain at all during my recovery. I admit, I wasn't driving long distances at first.
I think it's probably a good idea to practice a bit, make sure you can turn your head properly to see traffic, etc.
I used a pillow between my chest and the seat belt for a couple of weeks and then that got to be a bother so I stopped. I guess I should have kept using the pillow a bit longer, just in case of an accident, but luckily I never had one.