Owners of retail sites are sometimes concerned about including a generic descriptions on their site for the benefit of their readers because they fear the significance of their unique content will be reduced.  This very question was put to the Google Webmaster Helpline and the response in this YouTube video is extremely helpful.  The advice is simple, use descriptions of products that are going to help your readers in making a decision by providing unique content to do so.  Including the generic product descriptions that are found on hundreds or thousands of other sites is not useful and will dilute the ranking of your site in Google’s eyes.