For me it is. Of course I would have preferred to "just write Plim" and have the browser understand it.
How cool it would have been if the browser would understand different markup flavors (symbol-heavy, white space based etc.) and have integrated templating...
But it's ok, after the Makefile is stuffed with the pinned dependencies, I can forget about that and just write.
I use Slim for all my static site needs, it's supported out of the box with Nanoc which is my tool of choice these days - although it's more of a static site toolkit than generator.