My last employer used Iron Mountain. We had lots of tapes stored with them. A good percentage of the tapes were being held for 10 years. Overall we were giving them a pretty hefty bit of money just for the basic pickup-storage-delivery function.
Our management allowed end users to treat our off site backups as near line storage. This meant that there were some groups of end users, mostly in house software developers, that would make stupid moves with files on the servers and request that a backup from a given date be restored as soon as possible. This meant that we were asking Iron Mountain for "emergency" deliveries of our backup tapes about twice a week.
There were two things that were, in my mind, completely unacceptable. First, a nonscheduled same day delivery cost us $500. Then they would deliver the tapes at their convenience. I could request an emergency tape delivery at 9:00 a.m. and it might not be delivered until 7:00 p.m. It seemed to me that $500 was a pretty steep delivery charge. It also seemed to me that if we were paying that much money they should have had a special courier with just that tape deliver it to us immediately. They were certainly making enough money on these nonscheduled deliveries to have given the tapes to one person, have them get into a car, and hand deliver the tapes. What they did was to put the emergency delivery tapes on one of their trucks that would make their regular deliveries first, then deliver the emergency delivery to us.
Plus, the Iron Mountain boxes could not be locked.
In their favor I would say that they were very good about returning boxes of tapes when the retension period had expired. They were also very good about collecting boxes of new tapes on time.
Lastly, Iron Mountain recently had an incident of losing a customer's tapes.
That's all that I know to be a fact about Iron Mountain.