The third 0.94.0 RC is available for download here: http://people.apache.org/~larsh/hbase-0.94.0-rc3/
(My gpg key is available from pgp.mit.edu. Key id: 7CA45750)
HBase 0.94 is a performance release, and there are some interesting new features as well.
It is wire compatible with 0.92.x. 0.92 clients should work with 0.94 servers and vice versa.
You can do a rolling restart to get your 0.92.x HBase up on this 0.94.0RC.
The full list of changes is available here:
Please take this RC for a spin, check out the doc, etc, and vote +1/-1 by May 8th on whether we should release this as 0.94.0.