The important thing to note is provided in the 'technical details' section: "Creates a warm breeze until your car's own heating warms up helping with defrosting and demisting or you can warm your hands.".
"Warm breeze" was about it! Frankly, by the time it made a tiny (and I mean tiny) impression on defrosting, my car's own heating had taken over and done the job. The only good thing is it didn't cost an arm and a leg. I can only assume that the reviewers who gave it the thumbs up had a very low expectation and are easily seduced by clever-looking gadgetry. I should have checked the one-star reviews of a similar product on offer!