Security notices are good, too.

I’ve been using Wordfence for about a year now, and finally decided to upgrade to the paid version (which is heavily discounted if you need multiple keys for multiple sites). One reason is the security notices. They don’t hit you with every little thing, but when a problem is found in WordPress or a plugin they let you know about it.

It’s also nice to get notifications when somebody logs into your site, successful or not. If you’re running a membership site it gives you a real-time estimate of your site traffic.

And that’s all with the free version.