I have noticed a lot of sites replace the default OnePage checkout with 3rd party modules.
Two replacements I am familiar with is OneStep, and CheckItOut.
My personal opinion, from experience, is that the 3rd party checkouts are not worth the extra hassle they bring, mainly in extending their functionality.
Why are some so keen in replacing OnePage?
What is so wrong with it?
Best Answer
I've implemented a multi page checkout on Magento previously and to be honest it proved to be more hassle than it was worth. I suppose it depends a lot on how much functionality the alternative checkout needs to modify (and if it uses any of the existing onepage checkout code). Personally I'd always be in favour of keeping the checkout as vanilla as possible as it keeps upgrades and maintaining modifications to a minimum. Checkout is arguably the most important part of the site so you need to make sure it is as robust as possible and for me sticking with the default onepage checkout is the preferred way of doing that.