It is very easy to make quick progress driving in France, even by staying within the speed limits. I have driven from Menton to the Eurotunnel terminal (basically bottom to top) in a little over 13 hours, with a number of stops for a leg stretch (and petrol) and one 40 minute stop for lunch.
The lane discipline is second to none, roadworks are sensibly managed so that huge queues don't form due to the exclusion of one lane. In that one trip, with mixed weather, I experienced one hold up, at Lyon, really due to three or four large roads merging, and was expected (in fact I think Michelin build in a delay at Lyon in their on-line route planner).
Having left Folkstone terminal, I got about five miles up the M20 and joined a three mile stop-start queue as the three lane carriageway was reduced to one for...overnight verge works.
That said, usually when I make the trip, I'll stop over en-route, and spend the extra time allowed meandering down through different routes to my destination. Makes for a far more enjoyable time.