For prototyping this is okay. But for production I try to keep bloat as low as possible. I see this as service to my customers. A fat ui framework like this adds its very own complexity and as soon as you want to go out of the crud box you will have to add your own styles anyway.
I didn't compare the results between Purifycss and this bash script[1] yet. But this alternative, not intent to compete, does mainly the same detection e.g. including dynamic class adding detection.
Indeed an interesting tool.
If one keeps the site structure simple enough I think that the no-framework way might fit best. One doesn't have to go as far as for example this site http://bettermotherfuckingwebsite.com but it made me think about minimalistic css while keeping great device support.
I recently read the blog (http://.ws) of Adam Morse (http://mrmrs.cc) and it gave me some inspiration for my own css stuff.
