Beautiful! Adding the natural language parsing makes this so much smoother than Quick Entry (and looks better!). (Hoping Omnigroup keeps this Applescript exposed in 2.0...)
I added a Hotkey Trigger ("box") to the workflow so that I could access it via keyboard shortcut without even having to invoke Alfred. That also allows us to set the Argument field to "Selection in OS X". This pulls in any text you have selected before invoking the hotkey!
Here's the workflow with that modification: New Omnifocus Inbox Task
(Alfred imports Hotkey Triggers, but strips out the hotkey assignments, so you'll need to double click the hotkey step/box and press your desired hotkey. I used ⇧⌃A which works well for the scheme _mk_ recommends for his OF Task Actions workflow.)
Thanks everyone for your contributions to this workflow!
UPDATE 2013-06-21: fixed broken download link