It is a bit weird to use at first but I highly recommend giving it a shot.

I've built some complex UI's with the same class name styles (Basscss). 99% of the time I'm reusing classes and I don't have to write anything custom.

Prototyping is great once you memorize the classnames.. Just write HTML, no need to switch to CSS files.

If you're working with global styles this is by far the most scalable CSS methodology as of right now IMO.