Is this component based. Where I could pick the modal without all the forms. Or form elements without all the grid system. I'm dying for a pick what you need framework rather than all or nothing like everything else out there.
The most likely outcome will be to go with the "css in components" approach (w/ Radium, I expect) and maybe a base / "foundational" optional stylesheet for typography / etc. Still working it out though - all today's viable approaches have lots of pros and cons.
It has default styles baked into each component, allows granular overriding of styles at a component level, as well as global theme support.
I'm working on a project at the moment where I just want form elements :( but doing them myself because everything else is all of nothing.