WordPress.org

How do I create a checklist?

There's a new "Blogging Checklist" menu under the Settings tab. Go there and enter what you want.

How do I make checkboxes appear?

Just use a pair of brackets, and they will become checkboxes

Can I enter HTML?

Sure, go nuts. Okay, actually be careful. If you leave tags unclosed, you might make the administration pages behave weirdly.

Security Risks?

Yes, this plugin does allow you to inject HTML into the Admin pages. However, only an WordPress Administrator can change the checklist, so it's not really a big deal.

Why doesn't the checklist save its state?

That's not the point of the plugin. The checklist is just a reference card. The checkboxes are form elements, but these just allow the post author or editor to note which tasks he or she has already completed.