1. Standard informational call with internal recruiter, including some Javascript fundamentals questions. Recruiter was very down to earth and easy to speak to. Even had a few laughs :)
2. Received a link to a repository with a pull request to go through on my own. Next call was to go through the code with a bunch of developers to explain my thoughts on what was good/bad about it and how I would have done things differently. I was also asked to make a few smaller changes in the code. It was a very nice interview and I didn't feel too pressured or like they tried to catch me out on anything I wasn't sure of. Very conversational and where I got a bit nervous and struggling they helped me on the right track. Big plus for being very understanding.
3. Call with COO. Again very pleasant experience and nice call for them get an understanding of what I'm looking for/how I work/soft skills. I also got a chance to ask any questions I had.
4. Call with CEO. Same again, all positive and a very nice call. Got a very good understanding of the product and future plans.
All in all it's one of the most pleasant interview processes I've gone through (and I really hate interviews). I didn't have to invest too much of my time but yet it feels very clear what it would be like to work there, what they expect of you and what you'll get in return. Everyone seem really passionate about what they're building and happy in their jobs. The product is very exciting and I belive it's got a great future. Highly recommend - I'm 100% sure it would be a great place to work (even though I had to decline for personal reasons).