Loved Zenframe when I tried it out, it's only now that I have been using it for a while that I realize that it's full of bugs.
Some of them more major than others... such as getting stuck in "Saving" without actually saving the mockup. Two days of work lost...

Other major issue is that you will see since launch, there hasn't been any updates or new features. Objects are limited and bugged. Not worth the money.