Normally I have the deepest respect for the folks at TechCrunch, butPaul is completely wrong in this editorial. Here is what Paul said over at TechCrunch:
Those same people are now the ones who will buy iPads, or presumably any one of the myriad alternatives that will soon be flooding the market. But those people don’t want to carry around two tablet-shaped devices to help pass their commute, so they’ll make the sensible choice and leave their Kindles at home. Sure, the Kindle is unarguably the better reader device, but what many booklovers (myself included) have arrogantly overlooked is that it’s not competing on a level playing field with other ereaders. It’s competing against the whole universe of portable entertainment. “This ebook hurts my eyes – I’ll just surf the web instead.”
His argument can be summed up as "People will only want to carry one gadget". While he may be correct in principle, the argument he presents is wrong (based on my personal experience).
As a Commuter
I've been a commuter in 2 cities (DC and NY), and I can say from personal experience that no one will pull out a tablet and use it on the subway during rush hour. It's just not practical. You simply don't have the room to use it. Heck, most of the time you don't have the space to even get it out of your bag.
As a Tablet Owner
I don't have an iPad, but I have had tablets and I have tried to use them while mobile. Simply put, the iPad weighs too much and is too big. You can't use the iPad with one hand, and you can't even support it with one hand. It's much more likely that someone will read on their smartphone, Ipod Touch, or other handheld for the simple reason that they can be used with one hand.
P.S. I realized while writing this post that he might be correct. One point he missed was that a lot of iPad owners will also own a smartphone. They won't use the iPad during their commute, but they might use their phone. This would mean that the paired iPad+smartphone would replace the Kindle+ smartphone, and that might actually happen.