FYI - I rolled it back and all old forms were recovered.
You should add a notice to the upgrade that lets people know that all their forms will be lost and that recreating them is not an easy chore when you combine it with having to learn the new format/layout.
The latest version looks very cool but I made the decision to roll back after recreating three forms primarily because it took me 2-3x as long to create a form with the new layout. It looks very slick but functionally it is much slower than the previous layout. Previously you just scrolled down and the new version has to reload a new page, which is cumbersome and time consuming.
You should consider using tabs to break up the sections of the form but not having to reload a new page for each section. I use a jquery simple tabs navigation for a few of my own plugins that works like a charm.
Here is an article that show the basics:
Mine isn't exactly the same as his implementation but very similar.