Isn't the point of advertisement to help the audience form a view of what they're getting? Especially since its designed to skew audience perception to view the product in the most positive light possible? They aren't spending millions of dollars in promotion so people will 'wait and see'. They want people excited and energized and signing up for amazon ASAP.
Its quite worrying when something designed to make people like something, has the opposite result.
From what I've seen, and perhaps many others, is that yes, when promotion makes something look bad, its usually because its bad.
The term 'don't judge a book by its cover' worked in the era when book covers were tossed on and cheap. It doesn't really make sense when you have a multi-million dollar add campaign with experts and focus groups contribution to what is finally displayed.