While the speed limit is rarely any higher than 65 except in a few of the westernmost states (which you won't encounter between the East Coast and the Dakotas), in actual practice, almost everyone goes significantly faster on the interstates out in open country between population centers. I've set the cruise control at 80 for long stretches in the emptier parts of Alabama, Mississippi, and Texas, and been passed with regularity. I would advise you to pace yourself with the traffic; just don't go faster than the fastest other vehicle on the road at the time.

Driving on the opposite side of the road would seem to me to be pretty difficult. During my only visit to the UK and Ireland (for two weeks back in the summer of '04), my brother, who lives there, did all the driving. I would probably have caused an accident or two if I had been at the wheel.

As a passenger (sitting on the side of the front street that felt to me like the ":driver's side"), I knew I'd have been OK while driving straight down the road or street, but regularly felt disoriented at 90-degree turns. Perhaps it would have been less of a problem from the perspecive of sitting behind the wheel on the right ~ who knows?