The interview has three rounds, first is just a simple Skype pre-screening. It's not technical, it's just to get to know you a little bit and give you an opportunity to ask questions about the company and project. Then there is a one hour technical Skype interview. Apart from answering technical questions, you will write simple code pieces to a shared notepad. And if this goes well you get to the final round which longs four hours during which you meet four different people. Each will interview you for about 45 minutes, then you have a break before another one.
The people I've met were quite friendly and easy going. With each one I have written some code on white board. Typically, just one function or one data model that you were improving or modifying afterwards. You should think loud and be able to describe how you would test your code. Otherwise it wasn't difficult.
The feedback was very prompt after each round. I had the result the other day. Overall my experience is very positive.