Distinguish between "puffery" ("this baby hugs the road like a Ferrari") and statements of fact ("this Mustang accelerates from zero to 60 m.p.h. in 4.8 seconds"). The former is definitely an opinion that does not create a warranty while the latter is capable of empirical testing on the road. If the car cannot reach 60 m.p.h in 4.8 seconds, the seller has breached an express warranty.
Have you experienced examples of either situation in recent advertising? Please cite an example or two.