Google will show the same search results, but price comparison sites like PriceGrabber, Shopping.com, Shopzilla will include a message above the snippet: "This site aggregates prices from multiple stores". Snippets have a different formatting: a list of products and the corresponding prices.
The feature would be more useful if Google allowed you to restrict the results to price comparison sites and if the results were better formatted, for example sorted by price. It's also surprising to see that Google doesn't integrate the results from it's own price comparison site, Google Product Search.