Marco Arment says the iPad doesn’t need to do everything:

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 other side of the “if you needed a laptop before” coin is that iPads can serve as a laptop replacement for a number of people who never actually needed everything they got with a laptop but bought one anyhow.

Personally, I never want to travel with a laptop again, and I’d say travel is the big differentiator between laptop and iPad for me. If I were just sitting around at home, a laptop would be slightly less comfortable than an iPad and I’d like it less for Web browsing or playing the sorts of games I’ve come to enjoy on the iPhone OS. At the same time, I don’t think I’d be pacing the room because I didn’t have the iPad. Marco’s right that it’s not an essential device, to the extent you can do what it does with other devices.

But when we went out to the coast last weekend, I was really, really pleased and it was so much better than a laptop. I brought along my wireless keyboard because I knew I might have to do some work. The combined weight of the iPad and keyboard came in under that of an ASUS eeePC 1000, and when I was done using the keyboard it went back in my suitcase and stayed there, while the iPad continued to serve as a general purpose device that was a lot more comfortable to use sitting around in the cottage’s living room than an eeePC ever would have been.

Marco notes toward the end:

Accepting that the iPad isn’t an all-purpose computing device is going to be a slow process for everyone, including Apple. They can’t quite explain what it’s for, either, which is why the launch marketing, software, and accessories are a bit scatterbrained.

If you want to put it alongside a laptop and say “it’s not a laptop,” there’s no disputing that. But I’ll briefly go back to what I said about the iPad as a sort of satellite computer a few weeks back:

So I hope that the trend that eventually establishes itself is one of developers figuring out iPad editions of their desktop apps rather than iPad editions of their iPhone apps. I don’t need a super-sized tip calculator or Yelp client (Safari on the iPad is just fine for talking to things like Yelp), but I’d really like it if Gus would decide to take a whack at VoodooPad, Panic would look into bringing us a portable Coda, or BareBones would figure out something with BBEdit. OmniGroup has been planning to do just that since January, when Ken Case said “iPad or Bust!” I hope other developers follow OmniGroup’s lead.

These apps wouldn’t necessarily need to be the same as their desktop counterparts, but shouldn’t be “lite” versions, either, since that usually implies holding features back for marketing purposes rather than providing a scaled-down but fully functional version. It would be nice if they were accessory versions, I guess.

Meaning that the challenge for developers considering an app like that is less how to maximize the resemblance to a desktop experience their iPad apps bear and more how to identify the essentials of a given task (like editing text, or building a Web site) and deliver those things within the constraints of the iPad such that when you’re away from your big desktop computer you can still accomplish the essentials.

From my perspective, owning both a laptop and a desktop machine always seemed a little excessive, so while other people are deriding the iPad as an expensive luxury, I see it as a tool that costs much less than my MacBook did and does about as much as I ever used my MacBook for.