Sorry, but against distributed brute force attacks this plugin is quite useless. We had exactly this kind of attack starting last April.

So if you're not a single user on your blog and if you therefore cannot protect yourself by BASIC AUTH and .htaccess (what I consider the most effective way), you will be able then to use e.g. the SI CAPTCHA Anti-Spam Plugin on your login form and you'll be rather safe with even weaker login data of all your users.