We've used them for both of the last 2 years. Here are some things we've learned:
1) Buy radios with rechargeable batteries. They're more expensive up-front, but less expensive in the long run.
2) They're great for things like relaying the number of the player who committed a foul to the appropriate wing, reminding the crew of the number of time outs remaining after one is taken, asking the clock operator (part of the crew for us) to reset the clock, reminding all officials that a water/heat time out will be taken at the next clock stoppage, and lots of other situations.
3) After some trial and error - we decided that we would not use them after the RFP - we're focused (or should be) on the play that's about to happen
4) They are not a substitute for a crew conference. If the BJ and wing need to decide whether we have a catch or an incomplete pass, they don't use the radio for that. If both wings have a pre-snap flag, I still ask them to come in and make sure they both have the same foul
5) Agree on a way to acknowledge that a message is received. Even in a space as small as a football field, not every official will hear every message (at least not with our $25 radios)
6) There are some channels that are open and free to use by anyone. There are other channels that you can use only if you have an FCC license. I'm not sure how anybody would ever catch you, but there is a fine for using the ones that require a license unless, of course, you have the license.
7) It's unlikely, but technically possible, for anyone nearby to stumble onto your channel and listen to you, so it's always a good idea to be careful about what you say. You never know if the prom queen's grandmother is listening to you!
Hope this helps.