On the train, I only do "simple" things, like browsing the web, read e-mail, listen to music and watch movies - the kind of things that the iPad is well suited for. In fact, I noticed I did more with the iPad than I previously did with my laptop; now I also played games thanks to some great game applications for the iPad such as Real Racing HD and N.O.V.A. HD. I also read the latest issue of Wired magazine and TIME magazine using their own applications. I never did that using my laptop.
And no laptop I have ever owned has been as portable as the iPad. Not only is it small and easy to carry and use compared to any laptop and even netbook but using the tiny European iPhone charger, it is an amazingly compact travel companion. The iPad's own charger is a bit bigger and charges the device faster but the iPhone charger works well too and has no problem charging the device during the night. Not that you need to charge it very often though, the built in battery really gives you close to 10 hours of actual usage.
With a laptop, you really can't use it any other way than putting it on a foldable table in front of you and when you open the lid/screen, the seat in front of you always seems to get in the way. The iPad has no such problems and you can keep it much closer to yourself and that makes the 10" screen much more useful than a similar sized screen on a netbook.