During my interview, I met with three interviewers. The first portion involved answering a list of personality questions read by the interviewer. Most were pretty standard and asked about things like "what are you currently reading?", etc. There was at least one potentially unlawful question: "you're still not married yet, right?" (The fact that the role involved travel could potentially be important to married applicants, but employers still aren't supposed to ask about marital status under Washington state and federal law.)
The second portion involved assorted factual technical questions, whiteboard-oriented coding questions, and general brainteasers ("what would you do if you were the size of an ant?" or "how many golf balls would fit in this room?"-type questions). The interviewer attempted to negotiate salary while I was in the middle of solving a problem on the whiteboard, which seemed somewhat unprofessional. The third portion of the interview was about my interests and background.
A couple of days after being extended a preliminary (unofficial) offer, I was unexpectedly asked to come back in for another interview. This fourth interview seemed to cover the same ground as the others, but afterwards they decided to rescind the offer, even after having agreed on salary information during the fourth interview.