We are getting closer to a 0.5 beta. Cleanup of the bootstrap code is substantially complete; while there is room for further improvement (e.g. CASSANDRA-513), the foundation is there now for the other of our main goals for 0.5, load balancing.
We've also made a lot of performance improvements, particularly improving throughput on multicore systems. The remaining tickets scheduled for 0.5 are at https://issues.apache.org/jira/secure/IssueNavigator.jspa?reset=true&mode=hide&sorter/order=DESC&sorter/field=priority&resolution=-1&pid=12310865&fixfor=12314040 That and the completed tickets for 0.5 (https://issues.apache.org/jira/browse/CASSANDRA/fixforversion/12314040 -- summary so far at https://svn.apache.org/repos/asf/incubator/cassandra/trunk/CHANGES.txt) represent a fairly accurate picture of what to expect for the next release. -Jonathan