My 2¢ worth to OP:
I do an alignment on all my new cars as a rule - the reason? too many poor factory alignments (many brands including BMW) have worn out many tires prematurely. My brand new '12 X5d was way out of alignment at 100 miles when I had normal tires installed replacing the RFTs. Now the normal Pirelli Scorpion Verdes (19") have 28K miles on them and they look like they have another 10-15K miles left on them. They are worn evenly all around
Tip: Use an independent shop that does alignments all day/every day and has a late Hunter machine. Avoid the BMW dealer.
I don't rotate because IMO it does not extend the life of the tires in any significant way, and it has introduced balancing problems when I've done it in the past. On my rear wheel drive cars where the rears wear out much quicker than the fronts I simply replace the two worn tires first, moving the front to back and putting the new ones in front. Both of my current rear wheel drive cars (550i and NSX) have different sizes in the rear so no rotation and replacing two at a time is the norm with these
