Lots of posts if you search.
Haven't done brakes yet on the X3, but have done several sets on other recent BMWs (535, X5).
I replace rotors. It isn't worth my time to have to go back in and do them again when they are noisy. While it is technically possible to turn them, it isn't commonly done these days. The rotors don't have much material on them from new, as they are built for low unsprung weight, so they are generally considered a single use item.
I like to use OEM rotors, as the last set I bought had an anti-rust coating on the hat, and they stayed looking good. I have used jobber rotors, but there isn't enough price difference to make it worthwhile. Also, some jobber rotors have a poor cooling fin design, and the OEM ones are good. If I had to use aftermarket rotors, I would get Centric.
I use Axxis Deluxe pads, because I don't like cleaning wheels. If the dust doesn't bother you, just use the OEM pads as they are the quietest. Axxis Deluxe have very similar bite and pedal feel, no dust, and very little noise (but slightly more noise than OEM in my experience). Bedding them in is important. I get them from
www.zeckhausenracing.com, great service and a board sponsor. Bedding instructions are on their site.
Good luck.