First to say I think the beta plugin is awesome. What you have done (along with the main plugin) is give the WP community something 100% practical and totally superior to any offering directly from Constant Contact. The tools at ConstantContact.com are shockingly out of date.
The only issue I am having with form designer is getting it to save changes. I changed the width of my sidebar form from 300 to 200. The preview looks great - but pressing save does not save the changes.
Any help much appreciated. If you have a debug mode I can use to give you more info let me know.