Only have a few other interviews as comparison I would have to say that the process was of norm and highly professional.
Initially I applied only via their website and was contact within 2 weeks of posting. I had an initial phone interview with a Booz Allen recruiter who gave me information on the position and expectations from the team. After a short 20-30 min discussion the recruiter asked if I would be interested in interviewing with the team as she felt that I was a fit for the position.
About 1 week later I was contacted by a team member of the team I was to join and we had about a 45-60 min phone interview concerning my skills, background, education, certifications, etc... then we discussed in detail the duties of the position. He quickly realized I would be a fit for the team and the position and began to feed me the firm kool-aid, which was fine and I quickly bought it, however, I was still skeptical on whether the position was right for me.
After about another week, I was notified that they wanted to have a formal interview. I was interview in person by 5 different people from the team and HR, from team member, to lead, to manager. First interview focused on consulting skills, second and third on technical background, fourth was with HR, and the final interview was with the program manager. Each lasted about 30 min and were very professional.
I definitely felt that the interview process went great and that I would soon hear from the recruiter. After the formal interview, it took about 1 week for me to receive an offer with a start date within 2-3 weeks.