We have a CB in our RV. We have camping buddies that we caravan with and calling on the cell phones is actually not as advantageous as picking up the mic and keying to talk. We started out with the personal '2 mile' radios but the range within vehicles and vehicle to vehicle is very short. I bought a CB and installed it with a NGP (No Ground Plane) antenna then I bought a CB as a gift for our camping buddies.
We stick to channel 12 as it has proven to be fairly quiet on most of the trips we go to. Also, channel 19 is great for when there is a traffic jam. It is very useful to know what is coming and/or to know what lane to be in, etc.
The radio we have is a Cobra 29LXE with a weather alert radio built in.
I find having a CB while RVing to be very useful!