GoogleVideo has it online:
Moria opens a positive review with this: "This remarkable little film heralded the arrival on the scene of a tenderfoot new director". 1000 Misspent Hours says,
There’s a good chance that Duel is the best horror movie ever made for American TV. The sheer efficiency of it is breathtaking; barely a second is wasted anywhere, and there isn’t a single scene or minor secondary character that isn’t somehow necessary to maintaining the mood of escalating panic or keeping the story in motion.
The New York Times praises Spielberg. It has an 86% fresh rating at Rotten Tomatoes.