It feels kinda unwieldy.
Although I kind of get why it is like it is, but still. It's not easy to bring values (colors, etc) from another source without copy-pasting it manually or using plugins.
I guess when a designer uses it, drawing components basically by hand and then handing it off to a developer, it works. But in my situation, when I'm a developer and I'm mostly going backwards from an existing CSS framework, it just sorta curdles.