Although it is possible to collect the customer's billing address (using the 'address' option) using the Checkout form, it isn't (yet?) possible to add other, arbitrary fields.
For instance, collecting an email address would have to be done elsewhere.
Not having the ability to add an email address field to the checkout form is a real deal breaker for me. I wonder why they did not implement an optional email field.
For instance, collecting an email address would have to be done elsewhere.