I went through 3 very informal interviews, by traditional standards. The initial interview was an overall good experience, however it was obvious that the two employees conducting the interview weren't very experienced interviewers which resulted in a lot of awkward pausing -- this was hard to recognize and navigate as an interviewee. Interviews should not be easy, or predictable, however being able to gauge the impact of your responses as an interviewee is a large part of feeling successful in an interview.
The second interview went largely the same as the first, with the addition of a performance test.
The third interview, which was finally with senior management, was much more professional but still very vague -- in fact at the end of the interview I was still unsure if I was actually being offered a job or not.