[dnanian]

The Sandbox is basically for the "Pioneers" -- that is, the people with the arrows in their backs. If you're the kind of person who jumps on every update -- who installs things willy nilly and ends up in trouble, well that's when it's super useful. (It's also for developers who might need to run more than one version of the OS.)

If you create one, you need a partition for it. You then run from the Sandbox, as explained in the User's Guide, and install the program you're testing there. If all goes well, you know it's a safe update for you. If not -- you can simply boot back to the original drive, and it's no longer there. But, any changes to your "User Files" (that is, your Home folder) are still there.