I know with the EasyCare extended I purchased the dealer will do all the work to get the "pre-auth" work done. So if anything it may add 1-2 days onto the stay but they would give me a crappy 328 to drive so whats the problem.
My car has low miles and I don't plan on keeping it more than 3 years so I was able to get the extended for under 4k. If possible try to purchase the extended prior to your factory warranty expiring it will definitely lower the cost.
From what I've read Fidelity and Easycare are both good warranties. Both were suggested to me by my Service Manager at a good dealer. He actually had me go to another competing BMW dealer to buy it because it was "way better" than what they sold.
With all this I still don't know how well it actually works as I'm still under factory warranty a few more months.