This was a four-stage process:
Stage 1 - Hour phone interview with the team lead
Stage 2 - Hour and a half lunch interview with a panel of 5 or 6 managers and engineers
Stage 3 - Two and a half hour battery of questionnaires followed by an hour and a half meeting with an industrial psychologist
Stage 4 - Six hour interview where you are questioned by 3-4 panels of 5-6 managers and engineers
I made it all the way through to the six-hour interview. At this point, I was convinced that I was the sole candidate left, and that this would be them selling ME on the company. I was wrong. I was grilled by 4 different panels of managers and engineers.
I've been in my particular industry for 18 years -- to be asked to perform a task that a person with 6 months in the occupation should be able to do was beyond insulting. For the most part, the interviewers were friendly and welcoming, however there were a couple of condescending interviewers who seemed as if they'd rather be somewhere else. One of the more condescending ones felt the need to point out a typo in my resume as if pedantry is a prerequisite for the position.
Leaving that day, I felt emotionally exhausted by the experience but hopeful that I would receive an offer the following week. At 5:20 on Friday, I received a boilerplate HR email informing me that I would not be receiving an offer. I invested 12 1/2 hours in a process that ultimately led to a rejection with ZERO feedback, whatsoever. At this point in my career, my time is valuable. I burned an entire day of PTO to attend the six-hour interview, not to mention the time I invested prior to that.
The employees at this company obviously consider their time to be more valuable than that of the people outside of it. Think long and hard before applying to this company -- you will likely end up investing a lot of time in the process and end up being rejected with no stated reason.