We work in Scrum with the caveat that we don't have a potentially shippable product at the end of each Sprint, instead requiring several hardening/stabilization Sprints before release.
One of the reasons for this is that our chief UX designer prefers that we'll complete all the visual work (such as colors, fonts, exact layout and controls) at the later stages of the project. On one hand it makes sense because a feature with decent UI based on a wireframe is usually good enough to receive feedback from the users, so working too hard on the final visuals and styles is not necessary for risk reduction. It might even be wasteful if the feature fails at usability tests or if after further user feedback we'll decide to change the visual design for the entire system, including features that were already implemented. On the other hand with this approach we will have a list of features that are not completely developed, and with the final polishes being left out until the final Sprints.
What do you think we should do? Should we go with the recommendation of the chief UX designer or should we go for a potentially shippable product?