If you recently had a wheel (or two) off your frontend and you experience a vibration in the steering afterwards, chances are, you caught some dirty between the wheel and the hub.
This is even more likely if you're running one or more spacers.
McMark dropped my car off at my house last night (now *that* is customer service! ) and reported a shaky frontend at freeway speeds.
So today during lunch break i took the front wheels off and found that the second spacer on the drivers side was wobbling by a good mm left to right.
I cleaned all surfaces, put it all back together, made sure there was no wobble and voila:
Smooth like butter up to 120 ...