Actually, "Depending on where you saved it" doesn't really apply here. If you select download on any of the Apple trailers, it launches Quicktime and starts downloading it inside Quicktime. I looked for a "save as" from Quicktime but don't see it.
Specific work flows depend on the QT player used, Mac OS in use, and/or manner in which Apple has most recently programmed the "Trailers" web site. For Instance, today the files I tried to view would not open in either player directly so I simply recovered the URL for the files I wanted to view and manually opened them in both QT X and QT 7 Pro players under Mountain Lion. In QT X you use the "Export" option to save the original data to a local MOV file at the location of your choice. You can do the same thing using the QT 7 Pro player using the "Save" or "Save As..." options. File can also be saved as a reference file using the QT 7 Pro player.
I'm sure it downloads somewhere, but it must have a cryptic filename because I Can't find then either!
Also not sure how/where the data is currently cached locally. (Method seems to vary and it never seemed worth the effort to locate them or try to keep up with changes since more direct work flows are available.)