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
Someone commenting on their workflow using these tools would be awesome as well.
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.