What is it supposed to do?

I was reading the reviews for an iPad app before I decided whether or not to buy it. I noticed that 'good' and 'bad' reviews depended on whether the app did what the user wanted - not whether it did what it claimed to do.

 I thought that this is quite a good test for customer comments and complaints ... is the customer complaining because we offered or something that was not delivered (in which case we do something ... and quickly) ... or is the customer complaining over a feature or attribute we never claimed to offer (in which case we are polite but not accommodating).

 Is this a reasonable test?