Have you ever heard of the iPhone?
Enough said.
Well tell me this, sir, do you want to go on a train and be carrying a laptop, ipod, psp, cell phone, camera, etc.? It makes everything more compact.
The ipod and cellphone are small, so those two would be alright. The camera is optional, usually when you're going someplace new or having a party. I probably wouldn't take a laptop anywhere unless I plan on staying for sometime. I don't think I'll ever have a PSP or a DS, or any other handheld gaming system. Cellphone can be on the belt, ipod in pocket, camera in a bag or something along with the laptop. Really it isn't that much work, especially when all you're doing is sitting on a train.