I am a small business owner and I decided to use Adobe Business Catalyst for my own website and to build websites for my clients using this platform. Using this platform I have been able to create eCommerce sites and introduce/train my clients to the CMS so they have been able to update their own content and products.
Being able to use custom XML with web apps is non-existent even though they have been working on the issue for awhile. They even showed me a beta version of their web apps that would have done just that. That was about 2 years ago.