Extremely unprofessional and a waste of time.
First 2 calls were more technical conversations, looking at a bit of code and discussing a bit of design.
However after these, I was invited to do "the exercise". A 3 day coding exercise, with a demo at the end. They claim this is to see how you interact with the team, however it's not really possible to work on it during their work hours when working full time. So I worked on it in the evenings, when no one was online to be responsive to questions in time. It was a total $hit$how. It was an unreasonably huge hoop to ask someone to jump through at that point in the process. I did not enjoy it at all, was given no direction on what to do for the demo either.
Also, not once did they respond in the timeframe they said they would. They kept me waiting over a week for final response after the exercise when I was told I would hear the next day.
Don't waste your time on this process, not a company worth working for. I have never dealt with a more unprofessional recruiter.