Grueling. First you have a series of phone calls and an IQ/reasoning test. Then if you get past that, you get a Skype interview and then you're invited for an onsite interview. Onsite, most of your day is sitting around, waiting for the next direction but it was one of the most exhausting things I've done (outside of physical activities) because you feel a lot of anxiety during the waiting periods since you know they are evaluating you. They also cut half of the onsite group that same day which is really tough mentally.