There have been a long-standing discusses about these buttons. In particular - Positioning, Labeling and Visual Distinction. All these three subjects are closely related to the type of OS, the type of application /web or desktop/ and the specific scenario. The aim of these discussions was to see how we could make forms more usable & intuitive. And one of the items being discussed was the visual distinction of "OK" and "Cancel".
There are several reasons why we decided to change the look of "Cancel" button in the RadConfirm dialog.
First of all we wanted to visually distinguish the actions making it easier for the user to pick the right one.
Luke Wroblewski writes about this in his article Web Application Form Design.
He states that making the Primary action stand out more than the Secondary action is a good thing. In the findings of the usability test, he finds that it takes the user a little more time to complete the form if the Primary and Secondary action has a different design. But on the other hand it makes the user more confident and less prone to choose the wrong one. He suggest making the buttons in different colors or making the Secondary action a plain link.
Robert Hoekman, jr. recommends using a plain link for the Secondary action. His arguments for this is that it makes it clear which one is the most prominent.
In conducted tests it was found that users sometimes get confused by link, which acts as a button. We think that this might be because of never having encountered it in a form before. But as this practice gets more common in both web and windows applications, this should not be a persistent problem.
And as mentioning web and windows applications, we decided to keep the Button look of the "Cancel" for our "desktop" -like skins, namely - Vista, Office2007 and Outlook.
We are glad that you noticed this change. It is very important for us to know what you think on such, at first glance negligible topics. Your opinion is vital in the process of delivering the best possible solutions.
Vasil Yordanov, UX Team
the Telerik team