So happy i found this thread, that noise was driving me nuts. Same issue as you described ken, except that i could even hear it on the highway, as high as 130km/h. Anyway, lexus quoted me 80-160euros, depending on the time that they would take so i ended up doing it myself.
Lots and lots and lots of dust, cleaned the pads, the disks, calipers and especially the slider pins who where completely dried and stuck , greased them up real good and pushed all the air out from the little rubber boot.
Now the car feels better, the sound is gone (or i still havent heard it back again) and to add, the braking on the car feels a lot better.
I now no longer feel like im driving around a rusty wheelbarrow around town, yay!