I used to do IT on a ship. The combination of vibrations from the engine, salt water spray and wild power fluctuations is pretty lethal to computers. I imagine that a modern ship might not have those kinds of issues, but as our ship was built in 1914 we had all kinds of interesting problems.

A few people have mentioned that laptops are still too fragile, and I'd have to agree. My office is based out of a ship and we are constantly sending people off the ship into different nearby countries. The ship was in Malaysia, we had laptops in Thailand, Cambodia and Singapore. The ship was South Africa, we had laptops in Madagascar, La Reunion and the Seychelles. The ship is currently in the Philippines, we have laptops in Papua New Guinea and Australia. Though the users aren't always the most computer-proficient, they do try their best to take care of the machines. But one out of every five laptops that goes out comes back broken. We burn through motherboards, hard-drives, CD drives and power supplies. The only thing that never seems to break is the network card. Despite the fact that the point of the laptop is mobility, most hardware just doesn't seem to be able to handle repeated trips on planes, trains, buses, motorcycles, tuk-tuks, rickshaws, and the occasional camel, not to mention the inconsitencies in electrical currents.

I'd trade weight and cost if I could get some durability.