I use
Admin Tools to change passwords for users and have not had problems with it. It does not reset the password back to original but you wouldn't want that anyway. This one lets you make up the new password. It's easy to use though if you ever do it need it. I also really like the reset avatar option that comes along with it, but because my members are required to display a personal photo as avatar and not stolen images. Quick and easy to reset then!
Users can use the forgot password tool on their own though. You should need to be changing their passwords for them on their behalf.