They have been with me, for what seems to be forever. My permanent daily companions have been the notebook and the smartphone. The notebook has gotten faster and lighter with each generation and offered more battery life. The smartphone has gotten smarter and not is pretty much a mini computer which can be used to browse the send and receive email, browse the web, read and edit word documents and view, and in theory even prepare, spreadsheets.
Now comes the tablet... a new device has appeared making many, I suspect, consider a new daily companions. The tablet, whether the 9.7-inch iPad or the 70-inch Galaxy S are thinnest and lightest viable alternatives to a laptop that people had a chance to acquire. Notebooks that thin and light, have been available from time to time, the 1.6 pound 11.1" Sony Vaio X and a couple of 9 and 10-inch Fijitsu's come to mind. But the Vaio X and those small Fujitsu came at a fairly expensive price, while tablets are relatively affordable.
When I saw my first Apple iPad a few months back, it did not smile at me. It was a bit too big to be used while walking around, too big to be held with one hand. If got a device primarily to use it on on a table or airline seatback tray, I would prefer a small notebook. A smaller tablet like the 7-inch Samsung Galaxy Tab is something you can use in situation where a notebook would not be feasible or convenient to use.
I do not see the tablet replacing my laptop. I spend to much time preparing long documents to give up a physical keyboard. I does not mean that it would not have its own small uses. A small tablet is a less obtrusive device for taking notes during meetings and making references to resources during lectures and hearings. I can imagine, preparing spreadsheets might actually be easier on a tablet.
Walking around a mall with my wife doing Christmas shopping, I typed out this blog post on my smartphone while waiting in line to pay for gifts and waiting for packages to get wrapped, I cannot help but wonder if I there is actually room for something a both bigger and smaller.