There's a longer-term issue that occurred to me when thinking about pip's role as a "builder" or an "installer" (to use Nick's terminology). As I understand Nick's vision for the future, installers (like pip) will locate built wheels and download and install them, and builders (like distutils and bento) will be responsible for building wheels. But there's an intermediate role which shouldn't get forgotten in the transition - the role that pip currently handles with the "pip wheel" command. This is where I specify a list of distributions, and pip locates sdists, downloads them, checks dependencies, and ultimately builds all of the wheels. I'm not sure whether the current idea of builders includes this "locate, download and resolve dependencies" function (distutils and bento certainly don't have that capability). I imagine that pip will retain some form of the current "pip wheel" capability that covers this requirement, but maybe as the overall picture of the new design gets clarified, this role should be captured. Paul