I love 'em. It allows you to go do your own thing and still stay in communication with those you are travelling with. For instance, we (the guys) stayed on the ship while the girls went into town to shop. They finished their shopping and called us to tell us they had found a great little tiki hut bar on the beach to have drinks. They told us how to get there and we met them for a great beach afternoon.
Only get the ones that have the sub-channels or you will not get any use out of them since the main channels will have so much traffic on them they'll be a nuisance.