I have test driven many bikes and by far the Brose motor used in Specialized (and in my iZip Moda) is the best center drive e-bike system out there. I have 1500 miles on my bike and it is great. I asked on the Brose forum and got some responses. I think that I will ask the question on the specialized forum and try to find out what the reliability is for Brose motors.
The Brose system is the most natural feeling and quietest of the mid drive systems that I have test driven (Bosch, Yamaha, Brose). I liked the Specialized even better than my iZip but the Specialized is a lot more expensive than my iZip. I wish that I could tune things like you can with Specialized though.