<p>Is there a way to automatically increment the "minimum required version" fields in a ClickOnce deployment to always equal the current build number? Basically, I always want my deployment to be automatically updated at launch.</p>

<p>I suspect I'm going to need a some pre-/post-build events, but I hope there's an easier way.</p>

Are you looking for Application Updates?
Right clicking on the project in the Solution Explorer and then clicking Publish... is the wrong way to get Application Updates. You have to right-click your project and the click Properties, then click the Publish tab. Click the Updates... button and then check the "The application should check for updates" check box. There you can also specify a
minimum required version for the application.
(I haven't used that functionality but the Updates functionality is the core reason I use ClickOnce and it works great.)