Instapaper developer Marco Arment:

The iPad is a great device, but what’s it for, really?

Logically, it doesn’t make a lot of sense for most computer owners. In reality, if you needed a laptop before, you probably still need one. If you want to read novels, the Kindle is still a much better device for that. If you need a small computer for ancillary tasks that’s always connected and always with you, an iPhone is better (and you probably already have one). And, even though it’s a great deal for the hardware, most people will have trouble justifying the $500 entry price.

But using it is satisfying and delightful, and there are some things that it does better than a computer. That list isn’t as big as I, and probably most early buyers, initially assumed. And that’s OK.

The “single-purpose device” argument is a strong one, and often used in relation to the iPod. But the iPhone tends to fly in the face of that argument - it’s good at a lot of stuff.

What if you don’t have any computer or smartphone though? That’s what I’d be interested in. Can it work on it’s own if your main tasks are browsing & email? Maybe not:

For instance, if you’re using a hardware keyboard with the iPad very often, you’d probably be much better served by a MacBook Air.

Though it will cost you an extra $1400 to find out.