Yes, you need a $75. license for the GMRS. My radios are both FRS and GMRS, we've just stayed on the lower channels at this time. I have Motorola talkabouts, and they've got 5 mile range on lower and upper.
The main reason why I went with the particular model I have is that it listed 22 channels and 36 subchannels. If we're ever at WDW and it's getting crazy on the lower channels, we thought it'd be good to 'jump up'...we've never had to, though!
Leave it to DH, the Nascar nut, our channel/subchannel combos are all drivers (okay Martin/Kenseth, Park/Stewart, or Waltrip/Martin, among others) I'm in trouble if those drivers ever switch to numbers above 36!
Yes, the rechargeables do last all day...we even got a couple days out of a pair when we forgot to charge them that night. The model I have will take either the rechargeables or
AAA batteries, so I always carried some batteries (just in case).
Ironically enough, DH and I now have free mobile to mobile, so they aren't getting used nearly as much as I'd hoped, but I think as my kids get older, they'll be sent out with them when they go play. 5 mile range means there's no excuse in our neighborhood for "I didn't hear you, mom!"
Suzanne