Java code using Observables is bulky anyways because of anonymous functions, so it doesn't matter if durations are ugly, too ;-) I think RxJava's "mission" should be the a base compatible with everything, and will mostly be used from other languages. In Scala, for instance, we use [Duration](http://www.scala-lang.org/api/current/index.html#scala.concurrent.duration.Duration), and I'm very happy that it is compatible with TimeUnit. So I'd say first priority is compatibility, second is that it's "nice". But if someone comes with a solution which provides both, all the better.