I have driven many great routes - Scottish Highland glens and islands, Norwegian fjords, French Corniche, Italian Amalfi Coast and Alpine passes, New England coast roads, Ring of Kerry in Ireland and the Armagh coast road in Northern Ireland, spectacular mountain passes and coast roads on Crete amazing routes in Vermont. The Croatian route is up there with the best!
The road is in good condition and is well engineered. Graceful sweeping curves open up amazing vistas on almost every bend/ Towns and points of interest are well signposted. We travelled up from Dubrovnik to Split then down as far as Caytat near Dubrovnik airport as well as a diversion along a wine route from Ston and a ferry trip over from Drvenik to Hvar.
On the main E65 coast road, traffic ran at a decent speed but there were limited overtaking opportunities if you were stuck behind a heavy truck. Didn't happen often as, in this area, anything heavy between Ploce and the north would more likely use the motorway (cheap tolls). So many opportunities to get off the road anyway to visit charming little villages and harbours where the people are naturally welcoming and friendly.