I came across an interesting case study by Get Elastic on the Official Vancouver 2010 Olympic Store. They originally had a long multi-step checkout, but created a new single-page checkout with all the options on a single page. With A/B split testing, 50% of traffic was redirected to the original checkout, while the other 50% was served the new single-page checkout. After only 300 transactions, the winner was clear and they stopped the experiment after 606 transactions.
- Successful completion rate for the entire checkout process increased by 257.26%.
- Overall site conversion rate increased by 0.54%.
- Some unexpected improvements during this experiment, like an increase of 8.54% in the average order value!
Link to the case study: http://www.getelastic.com/single-vs-two-page-checkout
I want to emphasize that the Official Vancouver 2010 Olympic Store does not run on Magento/OneStepCheckout.