RC3 works with the applications I'm working on now and MLLib performance is indeed perceptibly improved over 0.9.0 (although I haven't done a real evaluation). Also, from the downstream perspective, I've been tracking the 0.9.1 RCs in Fedora and have no issues to report there either:
http://koji.fedoraproject.org/koji/buildinfo?buildID=507284 [x] +1 Release this package as Apache Spark 0.9.1 [ ] -1 Do not release this package because ...
