MITRE Internship for High School

For people who are in high school or college who have had experience in doing an internship at MITRE, would you please share your experiences (both the good and bad), what to look out for/preparation, and how competitive it is.
Thanks!

It is very competitive. Number of open spots depend on location - this year San Diego had only 2 spots - Not sure how many applied but it seems to be very selective.