http://www.overstock.com/ General Retail 1-Page 106 seconds
Overstock's checkout is an excellent example of how fast and frictionless a true single-page checkout can feel. Although the users do a bit of scrolling to complete the entire checkout, there is no waiting for a page to load or wondering how much further they have to go.
Further improvements could be made, however. Overstock gives no indication of either correct or incorrect form inputs until the user attempts to continue. No numbers, including dates, are auto-formatted, and fields inputs are not accepted robustly in general.
The Overstock Desktop Checkout complies with 60% of our recommended best practices.