Release Candidate 7 binaries are available at:
https://sourceforge.net/projects/bitcoin/upload/Bitcoin/bitcoin-0.5.0/test/
Difference between rc6 and rc7 : rc7 does not remove BDB (Berkeley database) log/* files, because that is causing un-readable wallets on some people's machines (all the reports were from people running 64-bit version of Linux, but that might have just been coincidence-- I could never reproduce the problem in any of my test environments).
What that means: old private keys can remain in a file on your disk even after wallet encryption, but they will eventually be removed. Details:
BDB closes the old logfile and opens a new one when it get close to 10megabytes big.
When bitcoin shuts down cleanly, it asks BDB to remove any unused log files, and BDB will remove all but one file from database/log.*
So: if you encrypt your wallet, unencrypted private keys will be in the old part of the log file. But after running for a half a day or so, BDB will close that old log file and open a new one. Then, the next time you restart bitcoin, the old log file containing the unencrypted keys is removed.
This seems like a reasonable compromise between security and safety for now; a better wallet encryption solution for the next version of bitcoin (for example, one that doesn't require shutting down and restarting after encrypting the wallet) is a good idea, but out of scope for this release.