I was interviewed for Causata team. Was asked interesting questions including coding exercise and a design question. I really liked people I met there. The interview was much more difficult in comparison with most companies in London but for me this is a good sign. It looks like they were looking for good developers. The projects they were working on were challenging and the experience you can get there will sit nicely on your CV for sure. The downside was money on offer, it was at least 25% lower than what I could easily find on the market, especially given the fact they were selecting candidates carefully, asked tough questions and looked for best people. But if you a talented junior developer you can definitely go there and get cool experience.