The DoD isn't saying much. We'll only know if these aren't compliant if they have to be used, by the way. There is definitely a chance of an air traffic disaster if these systems fail. However, we don't think there will be a wholesale blackout of FAA radar. In other countries, power will fail outright.
Emergency services are one of the key problem areas.
Where there's no water, there are frightened people. Watch for a disruption in Medicare checks to doctors, for example. If this lasts more then 60 days, medical practice offices will go bankrupt by the hundreds. The key, of course, is in knowing where these systems will fail. A failure in your VCR is no big deal.