GNU Taler is a nice software project. The problem with privacy-preserving centralized payment systems is that "writing software" remains the relatively easy part of the deployment puzzle: in practice you need to convince centralized banks and payment systems to deploy it for some application. Unfortunately, cryptographers have been trying to do this since the 1980s and DigiCash... with extremely limited success.

Decentralized payment systems have changed the equation and now we're seeing a great deal of progress in the area of privacy-preserving payments, some for better and some for worse. I wish Taler could find some applications over there, but the developers don't seem interested. Which is only fair.

(Disclosure: I've worked on decentralized private payment systems.)