With the new Get Started page [1], you can change the class names for the grid columns. Here's an example. [2]
[1] http://purecss.io/start/ [2] http://purecss.io/start/?cols=12&prefix=.col-&sm=35.5em&md=4...
[1] http://purecss.io/start/ [2] http://purecss.io/start/?cols=12&prefix=.col-&sm=35.5em&md=4...
Beyond that I'd say that Bootstrap includes a lot of what some might call "fluff," but take the CSS alone and I'm struggling to see the "less intrusive" part.