how dependable is the 2006 bmw 650i convertible
That depends. What is your definition of "dependable"? Any vehicle that is maintained properly should be dependable. If you get to know a vehicle and understand the noises and tendencies of the manufacturer to use ABS, which fails dues to heat and time, then nothing should come as a big surprise. I have stated that maintenance of a V8 is twice as costly and needs twice the attention of the inline 6. This is a fact for all BMW owners.