I'm stunned that there aren't more complaints here. I didn't find the old interface bad either, that said I'll move forward with progress but this is far from progress, this is a nitemare!
I've got two extensive Apps, JS/custom CSS and many objects and pages and action scripts.
The new builder interface isn't anywhere ready.
I can only imagine the vast majority of users are using simple spreadsheet apps, as this isn't now workable for a complex app.
Im totally gutted!!!! (to be blunt)