The Fast and Furious franchise has undergone a radical transformation since launching 12 years ago, with the changes following Justin Lin taking hold of directorial duties from Tokyo Drift (film three) onwards.
The series has made the transition from street races to include drugs, heists, and now terrorism, while lead characters Dom Toretto (Diesel) and Brian O'Conner (Walker) have gone from petty thug and law enforcer to wanted fugitives.
For me, five was the best of all of the films, but six gives it a run for its money, taking the stunts to ridiculous new heights (literally). You could, of course reprimand the film for its use of impossible feats, but that's the whole point of these films, right? To get bigger and more extreme, as demonstrated with the big and extreme - and always affable - introduction of Johnson in Fast Five.
It's highly recommended, you must go and watch it.