I work in a theater. We will have to spend between $6,000 and $10,000 to replace wireless microphones in the 700 MHz range, and there's no guarantee the new ones will work anymore, due to interference.
If the deadline was extended, we would be able to use the old microphones for the last show of the year and wait to see what happens during the summer, which is an off season.
I think that DTV is good in the long-term, but they could have done it without screwing over wireless microphone users (a high profile industry-- think of all the rock stars and football stadiums).