The API should be easily extendible to fetch other filetypes (eg. .msi or installer-exe). This is esp. important on Windows, where many users do not have a compiler-suite and thus can not build binaries.
Additionally some option "--prefer-build-over-version" would be helpful. This would fetch/install e.g. the pre-build binary package version 1.1.3 instead of 1.2.1 which is only available as source package.
Examples for packes this would be helpful for are: pygtk (et al.), pyopenssl, py2exe, psycopg2.