Technically this isn't my first CFMX7 site as CFLib, this blog, and my other web sites are CFMX7, but none of them are using CFMX7 features (yet). My first real CFMX7 site would be Celebrities for Charity. I'm not using many CFMX7 features, but I did replace two multi-step forms with a nicer CFFORM version. I love how the accordions allowed me to simplify the process quite a bit.
To be honest, this isn't a stellar site, but it used to be JSP and is now a heck of a lot easier to work with.
Edited: I should point out - I also use cfdocument to handle the receipts. Which is a small thing - but nice.