I did the Annapurna Circuit and Sanctuary last November and didn't think the road situation was nearly as bad as I thought it would be. Although compared to your experience in 1981 you might have a different perspective. On the first half of the trail I think I only saw 2 or 3 jeeps. However, there were a few sections that were under construction -- mostly on the other side of the valley -- and those sections were a bit noisy until getting past them. There was one instance where the construction was on the same side that we were hiking on and we had to wait about 10 minutes for them to finish what they were doing before letting us through.
Once we got to Muktinath, the situation changed and there were a bunch of jeeps. Since we were behind schedule and ended up taking a bus from Jomsom to Tatopani, the road only impacted us on the day we hiked to Jomsom. From Tatopani on to the Sanctuary and then out to Naya Pul, the road wasn't an issue at all. Not really sure what it was like between Jomsom and Tatopani, but I imagine that part probably had the heaviest traffic.