Really pleasant overall, very nice and comfortable. You need to be there on time. I recommend getting there 15 minutes early, they want you to show that you are interested in the position and serious about being there. Make sure you can talk about your resume in debt, if you are a recent college or still in college make sure you can talk about all of the jobs you've had (even summer jobs like camp counselors etc.) be sure to know your interests as well. For the HR interview most of the questions are about situations you've been in, like have you ever worked in a team, whats a situation you've been disrespected. You will interview with the people who are directly in charge of the service you applied for, make sure you have questions for them, they don't need to be seriously informational but should show that you are interested enough in the position to have done some research. If you have done previous research they will ask about it, make sure you can talk in detail about it, how many data points, protocols, etc.

Efficient and professional. After submitting my resume in response to the job posting I was interested in, I received a call back within a week and was in the MSKCC offices for interviews within two weeks.