Here's my take.
In your case, I would say the train with it's seats & 1 hr time period is more similar to an office scenario. Just like laptops extended the office to planes, long train rides & coffee shops Eee-like laptops extend the office further. The iphone is computing away from the office: The lift, the taxi, the meeting, the queue.
So to restate common wisdom: Whether or not you'll be able to work a spreadsheet or create a powerpoint on one is not as important as what new things you can/will do on one.
This guy implies using the Eee for calls, texts, music etc. I don't buy it.
If I had to stand up on the train, an Android phone or an E71 (or at last resort, an iPod) would be a much better choice.