Diablo 3 - Interview @ IGN

Of Balance and Barbarians is an interview with Blizzard's Jay Wilson at IGN:

IGN: We're excited for how balanced the five classes seem and how each of them delivers such a different experience. How did the team go about developing those five [classes]? They're all so different. They complement each other but they also work well solo.

JW: Well, a lot of it goes back to the core Blizzard class design philosophy where we look at each class and [ask]: what makes this class special? Why do I want to play it in the first place? What's the fantasy? This is something we ask a lot. And then when we target the key signature [fantasies], we don't let the other classes have those things -- we'd even go so far as to not choose a particular class just based on the fact that its fantasy steps on the fantasy of an existing class.

While we're at it, the Battle.net EU site points out they are still offering beta keys via Facebook.