[dbyler]

A hackish solution but one that works well...

1. Set up Quicksilver proxies to gain access to all your menu items (instructions here)
2. Set up a custom trigger for "Current application > Menubar items > Completed" (instructions on how to set up a trigger here)
3. Assign a hotkey and restrict operation to OmniFocus

A far more elegant solution would be to assign a custom hotkey in the Keyboard & Mouse Preference Pane, but I haven't found a way to assign a hotkey to submenus.

Note: in the current build, your project needs to be selected from the content window (not the sidebar) in order for the menu item to work. I've filed a bug report.