Update... just talked with the service manager at my local dealer. We have to have the car "emissions tested" (GAH! don't get me started on these stupid emission tests...), so I told him to take a look at the engine due to the vibration. The car is still under warranty. He just gave a slight smile, and said he knew exactly what I was talking about. He said there are a bunch of TSBs (Technical Service Bulletin) about this problem with Focus cars. I'll be bringing the car in next week. I'll let you all know what happens, it may help someone else.
This is still kinda sorta related to the engine stumble problem that is the title of this thread, right?... lol!