[la_fayette]

The look and feel of a UI is what is basically called a "non-functional" requirement. Altough this approach seems really helpful in specifying the app flow i think the small details which customers pay for, cannot be represented with this approach. Additionally, most customers I worked for might not understand these charts. Personally, I think tools like screenshots, click dummys or wireframes are more successful when specifying UIs for a customer. As a specification for a web designer it is helpful for sure...

[DaiPlusPlus]

A wireframe or click-through demo that pleases the client is not necessarily the best UI. (And the Best Customers are self-aware enough to know the Customer is not Always Right). Clients would gravitate towards that whichever impresses them personally - often by prior efforts made by competitors - but what looks snazzy and impressive often makes for a poor UX - consider the flashy CIA/FBI/LCARS UIs made for television and Hollywood, for example.

A resource like this is useful for when we, or UI designers we work with, are confronted by clients who want something flashy but impractical.