I've been building forms in the New Responsive designer for months. Once you get above the most basic complexity with show/hide rules, the Preview tab ceases to work properly. I'm forced to publish and test in production because the Preview tab doesn't reflect the correct operation of show/hide rules (and maybe other rules, I wouldn't know because I can't use the thing).
It's very frustrating because I love the Responsive designer otherwise and would love to not have to test my forms in production.
If the previewer doesn't reflect reality 100% of the time, it's totally worthless because I can't tell if it's an issue with my rule or the previewer and I have to publish in order to find out.