I did not enjoy the interview process with American Tower, mostly because it took SO long (over 3 months - see below) and they provided no feedback throughout the process.
+May 18 applied for job
+June 1 phone screen with recruiter
+June 5 phone screen with hiring manager
+June 22 in person interview
+July 7 second round in person interview
+August 28 follow up call from a different recruiter - I didn't even bother connecting with her because I had already accepted another job.
Overall a very irritating process.