There are various scripts on this forum which do a good job of listing OF statistics (total numbers for projects, tasks, contexts etc, plus numbers of those with a particular status like completed, on-hold etc.)
The only merit of
this script is that it is unusually fast.
(It also works when OmniFocus is not running - perhaps one can imagine circumstances in which that might be useful :-)
It works well with OF 1.8, but its speed depends on a short-cut which may prevent it from working with later versions of OF, when they come. (The schema of the OF cache is liable to be adjusted between builds, so this script may also stop working, and need to be updated, next time there is an update of OmniFocus).
If this happens, the script will simply suggest that you look for an update on this forum.
(attached as a zip below - can be
installed on the OF toolbar, or run on its own).
--