He likes the rich quality of apps (Reeder the first RSS reader he likes, Day One, etc.) and he is obviously carrying it around.. A LOT. And notice the way he's using it, like while sipping coffee, while exercising, etc. I don't know about you but I would rather have a tablet than carry a laptop (even a 11 inch MacBook Air, that's super light, small, and if you only put it to sleep no boot time) all over the place. We are not even talking about the apps (both in terms of quality of apps and the variety) that make things much easier and pleasant. You could more efficiently (by some measures) and more cheaply do all of what he does WITHOUT ANY COMPUTING DEVICE. But is that the point?
> haven't replaced any devices... and the tablet isn't good enough on its own
Did your cellphone replace your landline? Did your computer replace your calculator?
> the tablet is a luxury
Pretty much everything in the First World is a luxury. Visit Africa and you'll realize that. Visit the poor streets of India and you'll realize that. Anything that's beyond your basic needs is by definition luxury.