Version 0.8.1.1 of riak-scala-client is compatible with Akka 2.1.x (currently tested against 2.1.4) and Spray 1.1-M8.
Because quite a few people are eagerly jumping on the Akka 2.2 bandwagon, there is also a version 0.8.1.2, which is compatible with Aka 2.2-RC1 and Spray 1.2-M8.
Maybe. It is certainly not a priority for 1.0 but the http protocol does come with some encoding problems so we might migrate towards protobug in the future.
If you want protobuf support faster, please make your wishes known by creating an issue or a pull request!.It seems all the cool and appropriate names, like riaktive, riakka, riaktor, scalariak, etc. have already been taken by other projects. But there seems to be a common riak-xxx-client naming pattern used by Riak client libraries for other languages so that's what ended up deciding the, admittedly boring, name.
If you come up with a cooler name, please let us know and eternal fame will be yours!