I drive the road regularly and all I can say is you were lucky.
The trucks have all gone on go-slow since fuel became more expensive, the caravans are still there and if you are really lucky you can follow a pea harvester or a tractor and trailer.
The worst feature of the road is the number of protective islands at road junctions which they don't tell you about until its too late. I have seen a few people, unfamilair with the road, going to the right of islands - or in a couple of cases straight over them.
Then there are the locals who pull out in front of you at 20mph when they've already seen you coming, only to turn right about 50 metres further on.
The A17 has its moments but they are few and far between. I prefer it in the early hours of the morning.