Well, I must say I personally consider that a bad idea. Having the password case insensitive goes completely against the whole idea of password authentication. Good practise is on contrary to allow (and actually use) as many character types as possible. Any limitation put on accepted characters in the password significantly degrades the potential strength of the password. That is why security experts recommend to use a passphrase instead of a single password (that is, use multiple words separated by spaces, for example), mix letter case and use non-alphabetical characters. All these help to prevent from guessing the password. Any operation (such as changing the case, trimming the trailing whitespace etc) just makes the passwords weaker - for no good reason.
I do understand why the letter case in usernames should be ignored. But for passwords, I would definitely discourage from doing that.
