Moving away from 2.8.X for the broker build would be more feasible when folks running brokers in production are running them on 2.9.X or even 2.10.X and right now I don't know of anyone running a broker not on 2.8.X with any real volume (but that does not mean its not happening just I don't know about it). I will work over the next few weeks to start to pull more of this information together so its empirical and not assumed.
As it stands now folks are already running 0.8.0-beta1 in production and there is only a certain amount of beta that production operation folks will tolerate and upgrading from Scala 2.8.0 to another version for companies that have terabytes a day going through Kafka as a key part of their operations may not be feasible just yet.
While I agree with you 100% I also understand and appreciate how we need to support this project (lots of folks to support in different ways) and should be supporting this project for the stability it offers and rushing ahead has to be tempered with production support by the Apache Kafka community and PMC.
From my perspective the scalaVersion default is for the broker and the cross compiles are for different needs of producer/consumer (at least how I see it) and now that we are publishing to maven the default should matter even more only for the broker (again IMHO)
That all being said I looked through and get the patches now and will give these a shot in order using the 06/14/2013 dates
I also have some ideas about ways to making this available sooner for some things I am working on the next few weeks moving forward.
Thank you for the patches and patience. The best is yet to come!