I agree that no laptop has battery life that is nearly as good as that of the iPad. Still, current MBAs and MBPs hardly "require being plugged in all the time." Doing the rather limited things one can do on an iPad I can easily use my 13 inch MBA all day on battery without difficulty.I don't have a desk at home. Without a desk, a desktop is out of the question. A laptop is possible, but is a pain to use and requires being plugged in all the time.
For my at home, private uses, the iPad will suffice.