Helps with projects such as ride films - where there's a lot of geometry that gets processed needlessly. Basically - if an object isn't visible to the camera at a given frame - (like you've already passed it and it's behind the camera now) it's still getting analyzed during the preparing objects stage - wasting render time. This wasted time can become tremendous when you have a really large environment - as in when you're doing tunnel blast scenes for ride films. So - what you do is create a box that follows your camera - everything inside this box at a given frame will be given a visibility track with a value of 1 - everything outside the box will be given a visibility track with a value of 0 - so now objects are only visible if it's near the camera inside the box.
The only major differences between script packages are slight version compatibility issues - there are no new scripts added between the 3 packages.