Users wants something that will help with whatever they want done. And the quicker, the better. Interactivity is nice, but I never seen anyone complains about multipages applications.

> If you need to track all the otherwise transient UI stuff on the BE

So don’t add transient stuff? You send a page or a form according to the URL, the user does whatever it wants and either request a new page or submit the form. Each page is standalone like activities in an Android app. Anything transient is taken care of on the client side.