The basic checkout from prestashop can be hard to modify and not suit all the site's needs. This is a great addon with all the bells of a big website. You can set different looks and fields to be filled and it does the rest, no problem using all the couriers and payment methods you normally use.
It it not that complex when customizing, but it offers a great way to switch from that boring prestashop checkout. Also it is not translated in many languages and have to do it by manually.
Streamlined the checkout process in a prestashop based website.