Formal but not in a negative way. Still had a few moments of laughing and being relaxed. The interviewers were very professional. I actually had a good time with this interview, unlike a couple others that I had prior to this one where it was quite obvious from the beginning that I wasn't what they wanted at that company. In this interview it was very apparent that I was being seriously considered based on my resume and that the interview was (in my opinion anyway) what an interview is supposed to be, the verification that the person behind the resume is genuine and a good fit.

Interviewed at Career Fair, was a direct recruit/hire out of school. First interview team was two people, second Interview team was extensive (5 team members), and the questions were thorough about your engineering understanding of systems. Overall was nerve-wracking but the interviewers were nice.