Apple has already released a Leopard update called Login & Keychain Update. it addresses issues with:
- Logging in with an account originally created in Mac OS X 10.1 or earlier that has a password of 8 or more characters.
- Connecting to some 802.11b/g wireless networks.
- Changing the password of a FileVault-protected account.
It has the distinction of being the first Leopard only update. It requires a reboot. It’s available through software update (4.8MB for me) or as a 10MB standalone download.