I would never use a password that was e-mailed to me. Even for a game. I always dislike working with people or organizations that send my password via email As I understand it BattleMaster:
Sends a randomly created password to a new player
This password is used to verify that provided email addresses are valid
The password can be changes at any time
Changing your password does not cause it to be emailed to you
Aside from this initial password, passwords are not sent via e-mail
With this In mind, I think that explaining how to change your password upon the first log in, and even recommending it, is a good idea. Further, I think it would be cool if the game required new players to select a new password as they log in the first time. I think it would also be great to tell players up front that, aside from this initial password, BattleMaster does not send user passwords via email. It would certainly make me feel better.