From what I have read, apparently slotted/drilled rotors are prone to cracking. Also readings told me that airplanes don't use D&S rotors because they really don't want them cracking! I changed pads and rotors recently and got new ones from Rock Auto that were coated - as stated to avoid rust. They are great quality so far - but don't buy the cheapest - steel quality is better in more $$ rotors apparently. And yes there are many thoughts on why brakes vibrate, and that reason is mostly due to incorrect bedding-in procedures and buildup. I am leary of that because after I put on new pads and rotors (I always replace both) and bed them in according to the Mfg, there is no vibration and are fine for 40-50K miles. After that, if they start vibrating, it's when go down a long hill with the brakes on which really heats them up and the vib's start and goes away once the rotors cool. This hill is a regular drive for me and there is no vibration until they get older so if bedding-in was the issue, I'd think the vib's would occur at an earlier mileage and if a buildup was the issue, I'd feel it with hot or cold brakes. But that is just my 2 cents based on my observations in my car not anything scientific. Good luck with the new rotors!