I'm never sure what to make of these kinds of "leaks".

Even if it was genuine, it doesn't really tell you anything about Harmattan because it's basically just a multi-screen calendar application. It would be like having just the tyres of a new car model: important components but not exactly saying much about the car as a whole.

If it is real, I'm going to guess this is an in-house mockup and not really a screenshot.

It looks very nice, and I like the idea of moving around the application the same way you'd move around a website.