I feel obligated to see all Pixar movies, but I knew I wouldn't like this one very much. So I didn't go to the theatre to watch it, and it sat in the Netflix queue awhile.
As you probably know, it's set in a world where cars (and other machines) have taken the place of humans. You can't think about this too hard, otherwise you'll come to the obvious conclusion: that this is a result of a successful (but non-radioactive, non-destructive) Terminator scenario, where all the people have been killed off, and their mechanized artifically-intelligent killers just continue on. And (for some reason) doing pretty much what the humans used to do, taking over the buildings and roads the humans used to use, fitting into the roles humans used to fill. And never mentioning how it all came to happen.
And we're supposed to sympathize with these murderous things? And buy the action figures?
The plot, such as it is: a nefarious conspiracy is in motion to deny the mechanized world access to environmentally-friendly fuel. In opposition is the Aston-Martiny "Finn McMissile", an experienced British spy (voiced by good old Michael Caine) and still-wet-behind-the-fenders agent Holly Shiftwell (Emily Mortimer). The gang from the original movie, Lightning McQueen, Mater the tow-truck, etc. get looped into the plot when races using the nice fuel are scheduled. But the bad guys look to blow the cars up to make the fuel look bad.
In short, the plot is beyond dumb. The script is also not particularly inspired, with mindless action taking the place of the usual Pixar wit and imagination. It is Pixar, however, so the animation is great and the globe-hopping locations are impressively pictured.