There is one very bad situation surrounding ILocks. They can fail and they do. At our college for example one of our ILocks just decided to die. Right before one of my night classes. Rendered an entire studio useless. Band came in etc.. It was for Pro Tools with HD authorisation on it.
We only have the exact number of HD authorisations for the required machines that use them. Next day it was out of action for a while too greatly disrupting things. All sorted of course but created a bad situation. We will need to get a backup one now obviously. They have been running for years without a hitch.
Also in an interesting article in Audio Technology here in Australia a leading engineer was talking about working for Philip Glass doing a major tour. He refuses to use any in a concert situation because as he said they can stop an entire gig. Even with a backup there would still be down time while it gets changed over.
An Ilock failure might be OK in a non pressure home studio situation but it also has the potential to disrupt a high pressure situation. Just that one little thing doing it. I don't believe there is anything so important that needs it that cannot be found elsewhere.