Sure ideally, I've played with pyenv a bit but for my main machine I've kept my systemwide installs down to just enough to run virtualenv and virtualenvwrapper

Sure ideally, I've played with pyenv a bit but for my main machine I've kept my systemwide installs down to just enough to run virtualenv and virtualenvwrapper (everything else lives inside virtualenvs). For several situations though (like when Xcode command line tools stops working after a major OS update) it won't matter. You need a c compiler for several packages and having your stuff isolated per-user or using a non-system Python won't help that one bit.