It depends on your dealer service department and your SA. As I hear, some are cool about it, some aren't. You will put more wear and tear on the car than normal driving but unless you're hitting redline all the time (which you will if you race it) the service dept. won't know or care. Good luck, and have fun.
Another option would be to try the BMW M school. You get quality instruction and do it in M cars (and not yours either). Downside: cost.
I've been assimilated. 6MT/ZPP/18"/PS extended.