You might also want to consider what happens when it's time to trade the car in for a new one. If you trade it in to a BMW dealer, he might not be too happy that you've not got RFTs on there - that is if he noticed, perhaps he's more likely to notice if you've got non-OEM rims as well.
One solution for this of course is to keep the original tyres (and wheels) and swap them back on when it's time to trade in. Or sell the car privately. Or trade into an VW/Audi dealer :-o
Insurance is another good question ... personally I'd rather be completely truthful and know I was insured, so you probably should tell your insurance company if you change to a different type of tyre..? Could be bl**dy expensive if you wrote the car off and they refused to pay out.
2012 F10 520d M-Sport, Sport Auto, Imperial Blue, Black Dakota, Sun Prot Glass. V-spoke 281 Winter wheel package
Previous BMWs: 2009 E92 320d M-Sport, 2006 E92 335d SE, 2004 E60 530d ASE, 2000 E39 525d SE, 1997 E39 523i SE