Noise is one thing,but if your fork is chattering there's something wrong. Make absolutely certain the wheel is in the dropouts properly and the skewer is tight. Also check the tightness of your headset. Check to ensure the rotor bolts are properly torqued and that the rotor is true. Check to ensure the caliper is bolted down properly. Of course,all of these things should have been done by the LBS before you picked up the bike,but I've no idea what their QA procedures are.

If all of these things check out,it's possible you have contaminated pads/rotors,but it would have to be bad to cause this level of feedback. It is also possible something is amiss in the headset(bad bearings,missing parts) or even in the fork itself.