With the ability to set member only pricing and now the ability to set member only products, you have the opportunity to create a private catalog that is designed for and exclusive to your membership. For example, sell an add-on Wine Club membership to give Wine Club members access to exclusive and discounted wines.
To setup permissions on a product, simply go to the product (either edit an existing or create a new one) and set the visibility to "Active Members Only". This will now allow you to select the specific membership levels that have access to these products.
If a member doesn't have access to this product or they are not logged in, the system will prompt them to login to purchase. If they are already logged in, it will take them to your /memberships screen in an effort to upsell them.