I'm in the South-East, near Marseille.
It was very, very bad on Monday and Tuesday when the depot at Fos-sur-Mer was blocked; there are still very long queues at petrol stations in many places, but on motorways it's not as bad because the price is higher.
It took me 30mins to buy petrol yesterday, between arriving at the petrol station and driving off again, but I saw a 300-400m long queue at a petrol station in Aix-en-Provence this morning.
I think people are constantly toppping up for fear of new shortages, which doesn't help.
Diesel is harder to find than unleaded.
I don't think you need to cancel, but keep your tank at least half-full.
I'd keep an eye on the French media to see if other action is announced (road blocks, etc.), though Valls has said some bits of the legislation may be tweaked...