I have the asphault millings on top of my gravel drive. It's best done in the middle of the hot summer. Rake it smooth, then follow up with a heavy lawn roller or drive backwards with the bucket down and lip level. In hot weather, it can be pasted together and stays put. Benefits to me were a very much quieter driveway, no more dust, and no more raking it back onto the main drag. Its a bit softer at first and does eventually revert back to plain stone.
But, no more migration of gravel onto the grass shoulders.
In winter, I just drive on it a few times with snow on it. This gives my front low something to ride on.
Great stuff. The guy who delivered it made 1 pass with his tailgain chained open slighly. I really did not need to do a thing other than pack it slightly with the roller. $300 for 10 yards as I recall.