A bit fiddly - if you are new to all this website stuff and website security, then getting all the settings set correctly for your site can be a bit daunting, but overall the plugin is super!
Within 24 hours of installing the plugin it was already blocking attacks from China, Australia, the US & the Netherlands.
One gripe; If you are developing your site (i.e. adding pages, features, plugins, etc.) you need to highlight & copy your IP address from the dashboard page, then paste it into the 404 White List text field on the Intrusion Detection page every day (and do it before you do anything else)!! Otherwise you find yourself locked out of your own website; i.e. a blank white screen with the word 'error' in the top left corner. Dull, dull, dull!
Install it; you won't regret it.