Any number of reasons to choose a particular distro, but let me lump them into "system administration style" and "GUI style."

If you still like or prefer Ubuntu's system administration style (apt, packages, PPA, whatever), and you're just horrified by the desktop, then use another desktop or window manager.

    - Lubuntu (LXDE on Ubuntu, similar to Xubuntu)
    - LXDE and OpenBox manually installed.
    - OpenBox by itself manually installed.
    - Xubuntu.
    - XFCE manually installed.

I went with Lubuntu, pretty happy with it. It's a little unfinished, but not terribly so. And I still have all the apty goodness that I enjoy in ubuntu.

Or go upstream to Debian, or downstream to Mint, or over a branch with Crunchbang. Or a stream over to an RPM based distro. Or over into the next valley with Arch, Slack, etc. Get some strange with FreeBSD.

If the mainstream Ubuntu desktop sucks for you (it does for me), then moving some small or large distance to fix it is going to be much easier than suffering day in and day out.