This looks like a neat, light and fast alternative to Bootstrap for native looking hybrid and mobile apps. It's open-source and built with web technologies, so seems to offer great customizability. If you're looking to rapidly prototype apps, this could be worth checking out!

I experimented with ChocolateChip-UI a few years ago to quickly get simple list-styled app ported to iOS using Phonegap. It ended up being really slow and kept crashing. Has anyone had any success stories lately with it? I am sure it has improved from when I used it.