pip + requirements file + virtualenv (virtualenvwrapper) makes the setup of an development environment really easy. With virtualenvwrapper you can hook into different scripts, for example when you start/switch working on a project
"Private hosting" in this case, can be as simple as a plain-jane Apache server with some tarballs in a directory with listing turned on. Use -f to point pip to the directory. Instant private hosting. This is more or less how we publish internal libraries at work.
And of course some asshat downvotes because you bring up ruby...
I'll just point out that rvm isn't a pip for ruby. It only manages what version of ruby you're currently using and allows seamless switching. It comes in handy with ruby because of all the compatibility issues between ruby versions and rails versions. Pip is a sophisticated package manager that can be used with virtualenv to isolate where Python libraries are installed. They are indeed both good tools for development but serve different purposes.
RVM also manages gemsets, which lets you quickly save and switch the set of installed gems (packages). You're correct that it doesn't replace gem as a package manager.
Sure that's "the word on the street" so to speak, but is pip really so much of an improvement over easy_install (or buildout, no experience with it) ? Don't get me wrong, I like and use pip as much as of the next python guy, but I often get the impression that pip (and virtualenv) have an almost fanboyish charm; many/most of their advocates just ape each other and they'd be strongly pressed to explain why they are so much better than the alternatives (if they are even aware of them).