I have used nobeltec for 6 years.. I started with a regular laptop..and TRUST me those do NOT take the pounding and the moisture!
I bought a panasonic toughbook, i have been using it for about 5 years and it works great, takes the abuse etc.
The bonuses are... a GREAT big screen! Free software and maps..usually you can find it somewhere.
Negatives are..it is a laptop and not meant to be viewed in bright light condtions..
mine is a touch screen and in rough water or running.. well that it hard to do.. would be even harder with mouse.
You need a GPS or some toughbooks have a built in GPS antenna, i run a magellan GPS since it is compatable with nobeltec
I prefer actual push buttons like on a sounder.
Personally I would not recommmend using a laptop on a boat ...get a regular chart plotter..I am going to.