The easiest way to see the updates is to run the sample apps or sign in to My Apps. The Sample Apps are found in the documentation for each API. Choosing a Web-based interface like RESTful Java allows you to display an example in your Web browser window. Just choose a Sample App that uses the Payment API or In-app Messaging API and run through the Sample App to see the user consent updates. Alternatively, click on the Authorize button on the top-right of My Apps to see the user consent flow in action.
To get a good feel for the experience, access the Sample App using both a desktop and mobile browser.