Thanks, Ron.

So is is correct to say that if genuine mercedes pads and rotors are used, both replaced at the same time, and if they are correctly installed, then they should not squeal?

Also, what are the possible remedies? Let me summarize the results of my search on this forum. The following may help (some or all may be needed):
1) Apply anti squeal paste on the pads (I am sure they did that).
2) Use anti squeal shims on the back (and sides?) of the pads.
3) Check if the allen bolts on the disks are fully tight.
4) Check that there is no movement of brake pads within the caliper.

Anything else that can be done? I am sure someone has figured out a solution to this problem, since it seems to be solved for most of the vehicles on the road. A friend of mine just got his front pads and rotors replaced on his Honda at Midas - ZERO squeal from day one. So there's gotto be a clearly defined (or a set of) solution (s).

Thanks again, everyone.