OK. Let's say you're working on a textbook scrum project. You've got a scrum master collaborating with a product owner. The next sprint is UI-heavy – by the time your coders start building screens, you really want to have some idea what they're going to look like.
Who does the wireframing, and when? The product owner? Somebody supporting the product owner? The scrum master? If you have a UX expert, do they work alongside the coders after the sprint has started, or do they supply wireframes & mock-ups up-front that sit alongside your story cards and constraints to guide and inform the work the developers are doing?
I'm pretty sure we need some UX help, you see, but I'm really not sure where to apply it…
EDIT: Let me rephrase the question.
How do you deliver consistent, high-quality user experience on an agile project?
Best Answer
The interaction designer
UX != UI You need a experienced interaction designer to deliver good user experience, contrary to popular belief that is not a programmer. For all of you programmers who think they can do UX (that includes me) let me say this. Getting good at interaction design requires at least as much time as getting good at programming. How much time have you spent doing pure interaction design?
In the initial phase it's the interaction designers responsibility to:
During the project it's the interaction designers task to make sure that those guidelines are followed and address any additional issues that will arise (and they will).
Many programmers will take afront to this approach I'm sure since everyone feel that they're the exception that can design "wonderful" interfaces, you're probably not. On the other hand a good interaction designer - programmer relation is often very nice for the programmer as well as they don't have to fight against a "stupid specification". Unfortunately good interaction designers are hard to find in my experience but they are out there.
As always I deeply recommend Alan Coopers books on the subject ("About Face" and "The Inmates are running the asylum")