Got a point to me honest, I see even the guys with Sony e-readers getting interesting looks on the train...this will be infinitely worse.
It wouldn't be the looks that would bother me, it's the over the shoulder watchers that do. I'm sure everyone who commutes is familiar with people trying to read the newspaper that someone else is reading.
I've always found that if I'm watching a video on my iPhone on the train, that quite often if there are people sat or stood nearby with nothing to look at themselves, that they will be watching your screen. I often try and angle it so that they can't see it, but that's not always possible.
So given a device as big as the iPad, you are going to have loads of people trying to get a look in at what you are watching.