iSearchBetter seems like a much better interface than bigscreenprices.com, which needlessly uses AJAX to request the search results, with no indication that anything is happening. iSearchBetter is more organized, and they also provide more detailed results – pictures, descriptions, etc.
The front page of iSearchBetter says it best, on why Amazon customers need a search engine that only returns Prime items:
I love Amazon.com, but I hate searching their site. Their search engine returns thousands of used products from random 3rd-party sellers in hundreds of seemingly-arbitrary subcategories, and I can never find what I want.
It’s beyond me why Amazon doesn’t provide this functionality themselves, but I imagine they don’t want to directly advertise the items that ship free.
Hat tip: Amazon Web Services Blog.