Jeff and I have re-written the install script to use mercurial. This involved adding in an optional bzip2 installation, as that was a sticking point for several machines, as well as re-organizing it to install bzip2 before Python and then hg before yt. If you get a chance, I'd really appreciate it if you could try running it:
There's a "branch" name at the top that governs which yt branch gets cloned and updated to in the installation section.
Any feedback would be constructive; we need to replace the current install script pretty soon, so let me know if this does or doesn't work!