There have been several thoughtful pieces recently on device form factors and what you can and cannot easily do with tablets versus laptops versus smartphones.

Richard Gaywood says the iPad (it’s an Apple site) is “heavily skewed towards, but not entirely about, consumption” rather than creation. His observation is based partly on app statistics, partly on the lack of a keyboard (if you add a Bluetooth keyboard, he argues, an iPad becomes as bulky as a laptop), and partly on weak multitasking and the lack of an accessible file system.

Tim Bray currently carries a laptop, a small tablet (a Nexus 7 I guess) and a phone. He does not seem to be considering abandoning the laptop, but suggests that he might be able to manage without a phone:

I spent several months back in 2010-11 carrying around the original Samsung Galaxy Tab, which may have only been Gingerbread, but included a first-rate phone, and my handset rarely left my pocket.

John Gruber writes at unusual length about why Apple might or might not do a smaller iPad.

On the eve of the Windows 8 launch this is an interesting discussion. Windows 8 will renew the debate: is a tablet all I need, at least when travelling? And where will Google’s 7” Nexus fit in? I foresee this selling well simply because it is great value, but will it be packed in the flight case alongside a laptop and a phone, or left at home, or could it even replace laptops and bigger tablets?

We in the the great unknown; but I will make a few predictions.

First, laptops and indeed desktop applications (that is, not apps) are in permanent decline. That does not mean they will disappear soon, just that they will be used less and less.

The implication is that tablets will be used for content creation as well as consumption, and for work as well as for play. Will developers and designers still want huge multi-display setups? Yes, of course; but most people will get most of their work done with tablets.

Second, that unadorned tablets will win over complicated solutions like laptops with twisty screens (the old Tablet PC concept), styluses, transformers, and the like. My guess is that we will see lots of clever and expensive Windows 8 x86 devices that will only achieve niche sales. The ones that succeed will be the slates, and the traditional laptops.

Third, there may be merit in the keyboard case concept, particularly when the keyboard is very thin, as in Microsoft’s Surface with Touch Cover. On the other hand, keyboard cases that make tablets into laptops, like one I tried for the iPad, also tend to give tablets the same disadvantages as laptops: clam shell design, difficult to use without a desk, and so on. I have found that I prefer a loose keyboard in my bag. It does not take much space, and does not get in the way when not needed.

What about mid-sized devices like the Nexus? I am not convinced. They are too small for all your work, and too big to be phones. The large-size Smartphones like Samsung’s 5.2-inch Galaxy Note sort-of work: they sell to people who do not mind having a large phone. But most of us will end up with two devices in constant use, a phone and a tablet. In the office or study, add a large screen and keyboard to taste.