Category pages are very important to help the shopper want to keep searching. If they have an image banner at the top, it needs to have a clear message explaining the content grouped on that page. These pages should also have enticing, best seller or significant new items featured at the top. If a category page doesn't have a clear message it creates confusion and the shopper may move on.
Product pages have to give the shopper all the information they will want. I often say the customer doesn't read all the copy points but if they want information it needs to be there. I believe that the copy points need to be organized the same in each category so the shopper can easily compare items. The customer expects to have all the image views they want to see for each item. Images need to show all sides and features. I also believe boxed items should be shown in case the shopping is looking for a gift. If the product page doesn't have the information and images it needs they shopper may quickly move to Amazon to find out more.
The big sites understand that they can't create confusion points; however, some newer sites are just scrambling to add items. Sites need to take the time to add items and pages correctly in order to keep customers on their site.