3D touch is unreliable and not intuitive. When do you poke, when do you peek, how much do you press ... and on what ?
An idea that sounds good on paper ..
I disagree. There may be some instances where you don't know what it's going to do, such as on App Icons that you haven't done it on before, but for most things it's pretty obvious what's going to happen.
Is there a link to another webpage? It will Peek a preview of the page. Press a little harder and you'll pop into the page.
A link to an address? Peeks up a preview of the address in Maps.
A phone number? Pulls up a menu to either call, text, or save as contact.
An email address? Pulls up a menu to message or save as contact.
Those last two are especially nice. Trying to add a number to a contact is a lesson in patience. Trying to select the number without accidentally clicking on it or getting the selector to select more than just one group of numbers is a pain. To be able to do it with one click is a huge improvement.