I am not a security expert, but as I understand it, passwords sent in the clear are vulnerable to being intercepted. Even if users of your site don't have much to worry about from those accounts being compromised (this may or may not be true), lots of people use the same password for more than one login, so their accounts on other sites could be compromised too.
That's definitely a significant security risk, even if it wasn't being explicitly labeled before now. It sucks for independent website operators like you, but I'd probably blame your hosting for making it difficult to secure your site rather than browser vendors for protecting their users.
