I've been considering getting one as well.
I can say that if you want to go the distance, using a handheld with a rubber duck antenna transmitting a max of 5 watts isn't going to get you very far on VHF. The problem isn't so much the radio output power wise as it is the lack of gain from the antenna. If you were to pair a handheld on a decent say 1/2 wave antenna I'm sure you would have far better results. That said if I make the plunge I'll probably go with a mobile and a fiberglass whip. If nothing else I always thought a boat with a big whip just plain looks cool and you can never have enough radio and electronics gear
Overton's has a package deal right now, a Cobra 25 watt mobile, 8' glass Shakespeare antenna w/mount for 149.00. That seems like a pretty good deal.