Not, “put this on my iPhone now” good but “wow, that’s interesting and must’ve taken a lot of hard work” good. Lifehacker explains:

You can now grab the theme via an app on Theme Outlet. Here’s how. (And make sure you have Dreamboard installed, as this is a Dreamboard theme and requires it.)

  1. Open Cydia
  2. Tap Manage Sources
  3. Tap Edit, then Add, then add source
  4. Go to the Changes section and install Theme Outlet
  5. Close Cydia, go to your home screen, and open Theme Outlet
  6. Browse for OS X Ultimatum and download it from there
  7. Open up Dreamboard, browse for the OS X Lion Ultimatum theme, and install it.