After a pleasant phone interview (with a substitute interviewer: the planned person was unavailable?), I was asked to return, by email, a small "homework" assignment. These always surprise me: they're either so simple that even if you can't complete the work yourself, it's trivial to find answers on the web, or in a textbook; or they're so complex/involved/specific that it feels like the company is asking for actual work without pay.
Nevertheless, I passed that, and after a 2-week delay, was asked to spend a few hours doing in-person 2-on-1 interviews. These were also mostly pleasant, although my phone interviewer was also present for one of these. One thing that came up, though, was that the skill I was being interviewed for (and which I consider my strength) was planned to be obsoleted by installation of a new process. Hmmm ... ???
About 10 days later, I received a call telling me they had decided not to proceed any further.