They just turned my slotted rotors for me when no other shop around me would. Now I can make it to CLub Wars with the DBA rotors instead of the stockers.
You can but you just have to be careful to not trash the bit. Most places try to do it too fast and set the depth too much and the tip hangs on the slot.
You can, its just hell on the tooling. Most places will give you a :fawk: Still, if you can find a shop to do it, more power to you.