The first phone interview was about 40 minutes, and it consisted of pretty general questions (e.g. why Mathematica? walk me through your resume, strengths/weaknesses, etc.). The interviewer was engaged, but it's clear he had a list of questions to hit. The second phone interview, which took place two weeks later, was about one hour and was fairly similar to the first. The main difference was that it involved HR specific elements, such as anticipated salary. After a bit of follow up for feedback from the HR coordinated, I was told I would have an in-person interview. The company paid for my flight. The in-person interview was an all-day (from 9-3) round of meetings with 9 individuals. Most were one on ones, but two interviews was with two Mathematica employees at the same time. Everyone for the most part was fair and interested in what you had to say. A few people were extremely intense in their questioning and came across as more aggressive, like an exam instead of a conversation to see if you're a good candidate for the job. However, overall I felt good about the experience and my performance. Although I had frequent communication with HR, it took well over a month to get a decision. I was told they wanted to hire me, but that they couldn't at this time because of a lack of work, and that they would like to keep open the possibility of my joining the team in the future.