I hadn't noticed this yet, probably since we just did the 6.5.4 Domino upgrade, but there is now the option to set custom password policies for Notes users. Thanks to some Italian legislation this has been added. So now you can set minimum and maximum lengths, whether or not usernames can be part of the password, force special characters, numeric characters, etc.
You can also force a user to change his password the first time he logs in to Notes! I think that's a very good reason to check this out.
I plan on checking this out to confirm that everything works as expected and possibly implement it once I go over it with our security team.
Read the technote documenting this new feature.