Initial phone screen is short and sweet, looking to ensure you fit the job description. The next steps, a formal interview, and the invitation to interview on-site, are very detailed to observe your answers as well as you reactions to questions, and give the interviewers (usually 4-5 minimum) a chance to scrutinize your personality, ability to interact with others, and most importantly how you handle certain aspects within the position at hand. Overall, the process is sound, but the length of time between each of the steps is very long; it seems as though you may never hear from them, when they finally contact you.

Well structured. Complex math and logical questions. Well organized. Smart people to interview with. Plenty of questions to determine your skills and IQ. Definitely above average. They hire only the best of the best.