This is excellent news. Questions though...does Riak CS need its own dedicated Riak cluster or can you use "its" Riak nodes directly in the usual Riak fashion? If so, is it possible to access the CS-created chunks directly? (Not saying that is a good idea...just trying to understand how Riak and Riak CS fit together.)
Riak provides key-value services for Riak CS, and there's nothing stopping you from configuring the same Riak cluster for both the Riak CS application and another application.
Riak CS doesn't use any Riak functionality you can't use yourself, so accessing Riak CS-created chunks is easy because that's what Riak CS itself does. The source for how this works is at https://github.com/basho/riak_cs/tree/develop/src in case you want to play and have fun with that.
This is true, but Riak CS has special configuration requirements for the backing Riak cluster that might make it not the best choice for combining with your typical Riak applications.