I think this is a good insurance to have.
I didn't have it for my prior 6-series, bent a rim, and paid 700-800 dollars to have the wheel and tire replaced (they were runflats on the 645Ci).
I bought the tire insurance for my M5, got a flat 2 weeks after picking up the car and got the tire replaced. Well worth the cost, about 500 dollars and change for 4 years of coverage.
The insurance covers whatever is on the car, does not have to be OEMs, and includes the wheel as well.
Current rides: 2010 CTS-V sedan, black raven; 2010 Cadillac Escalade ESV, black raven
Gone but not forgotten: 2008 M5, metallic sapphire black, SMG; 2004 645ci, metallic sapphire black, SMG