I'm really excited by RiakCS (now rebranded as RiakS2) because when it works, it offers a powerful on-premise version of S3. I've been integrating it with Cloud Foundry for about a year now, repackaging it to deploy with BOSH, but it's been a constant source of frustration.
From an operator perspective it's incredibly hard to install and configure - the onboarding process to create a cluster from scratch is terrible and the outputted logs are often little more than erlang stack dumps. As an example, I've already spent days trying to get riak-cs 2.0 running on a stock ubuntu 14.04 machine. It should not be this difficult to stand up a product out of the box.
Basho's support engineers are generally well intentioned but often their response is "run the following erlang command, and reply to us with the response (also in erlang)". As an operator, I have no idea what effect the provided commands have on my system, now what the output should tell me. Similarly, it took months for their support/engineering team to answer a support ticket about garbage collection - eventually providing us some defaults such that RiakCS would perform garbage collection out of the box. They could not tell us why these settings would work, nor any side-effects of changing low-level parameters.
From a product perspective, Basho do not appear willing or able to support the open-source community around their products - typically every answer we've received boils down to "it depends on your use case" and effectively "it should work, I don't believe you are seeing the issues you are raising".
I really hope this 're-positioning' results in more support for operators and the community in general. RiakS2 has a lot of potential and I hope Basho are able to realize this.