I always find it fascinating when people criticize something, i.e., a product or service such as UberBlack, without having any direct, real world experience with it.
The €2.50 maximum difference & €.80 minimum difference that was pointed out is insignificant to me, especially in light of the great service I experienced with UberBlack. Even with the "higher" cost differential, I would choose Uber.
Still waiting to hear from someone with actual experience with UberBlack in Germany or Europe.