I just removed this plugin from ALL of my WordPress installations. I tried to login to one of them today and was told I had to wait 20 mins due to too many login attempts. I had never had a login problem with this particular WordPress installation so when I encountered this, I wasn't very happy to say the least.
Additionally, it never sent any e-mail notifications to the administrator account, letting me know it was locking out IP addresses due to failed login attempts.
Between these two issues, I can't recommend using this plugin. I _can_ tell you it works since it locked me out of my own WordPress installation for 20 mins. :)