Typically, there's a deductible and yes, everything that needs to get repaired has to be pre-approved first and that can def be a hassle so know what you're getting into. Other questions to ask are what their warranty excludes because if it excludes all of the major components then what's the point? i.e. i-drive, tranny, engine, turbos, diff, etc.
i recently had a problem with my car which resulted in the dealer replacing 3 injectors and the dme (which is basically the car's ecu). I'm at about 62k miles and at first they didn't realize that I have the BMW ext warranty and they wanted to charge me like $500 just to start looking for the problem. Once I told them that I have the BMW ext warranty, she was like oh, I see and said they get started on the car immediately. (you can do a search under my name for the most recent problems that I reported.) So I would say to keep this scenario in mind when deciding. Of course, my repair bill paid for the ext warranty and then some just on this one occurance and of course owning a BMW past warranty is a big no-no. Good luck.
'08 Montego Blue 335i, auto, grey leather, aluminum trim, 50% ceramic Llumar tint on all windows except windshield - all options except active steering, active cruise control, and HD radio
'01 Lexus IS300 - gone but not forgotten