[Toadling]

You might also consider trying this hidden preference (paste into Terminal and hit Return):

defaults write com.omnigroup.OmniFocus LeaveEmptySelectionEmpty -bool yes

This will make OmniFocus show nothing in the main content area when you have nothing selected in the sidebar (instead of showing everything). Then save your perspectives with no sidebar selection.

With this simple change, I can switch perspectives instantly. Of course, nothing is displayed in the main content area, so I have to make a second click to manually select an item in the sidebar. But even with the slightly annoying two-click process, OmniFocus still feels much snappier.

I'll also point out that this "no sidebar selection = empty content area" behavior is the way many other Mac apps behave as well (e.g. Apple Mail and Yojimbo).

If you don't like this setting, it's easy to undo too:

defaults delete com.omnigroup.OmniFocus LeaveEmptySelectionEmpty

BTW, you should relaunch OmniFocus after setting the hidden default (or better yet, just quit OmniFocus while you make the change).

-Dennis