Yeah, just leave it in OD. About the only time you'd ever wanna put it in D is if you were driving on a rolling road at speeds near OD threshold, and it kept shifting in/out of OD and was getting annoying. This doesn't happen much. But on rare occaisions you might find that happening.
You can use it for a little additional speed control in certain instances too. A place near here is a known speed trap, and the road is gentle rolling hills with a 50 mph limit. In OD, it'll roll upwards of 60 mph on the down hill pretty easy, so a lot of the time I'll just put it in "D" and set the cruise at 50, and it won't pick up speed quite so fast downhill, so I don't have to watch the speedo so close.
About the only other time I use "D" is if I go flying by a state trooper well in excess of the limit, I'll drop 'er down to "D" to knock off some speed without hitting the brake.
