For the site I'm developing, very few users will register themselves. I'll be creating most of the users as admin and then sending out notification e-mails to invited users. This plugin will make it quick and easy for users to update their passwords the first time they login. I was able to get it installed and tested within about 15 minutes. Quick and painless! The only reason I didn't give it 5 stars is because the bulk action option to expire multiple users' passwords at once seems to be missing from my install.