Have you had your caliper mounts faced? Due to mass production and low machining tolerances, alot of the caliper mounts are not perfectly aligned to the rotors. Most disc brake companies tell you to have the mounts faced which aligns the rotor and caliper, preventing pre mature wear, noise and poor performance. I have Shimano deore's and had some noise problems after first purchasing my bike. My bike shop told me they needed to be faced. I couldn't understand why any company(all of them they said), wouldn't do that themselves. But after having them faced I have had no problems what so ever. I have over 4,000 miles on my bike and have only replaced the pads three times and have had no noise except when they have gotten wet. Cost was about $30.00 approximately. Well worth the investment!