Facebook and Gmail both have production and consumption. A device that excels at consumption and is inadequate for production will not serve as a replacement for many people. It sounds like the iPad is adequate for at least some limited typing, but it remains to be seen whether it's adequate for what most users do.

The bigger critique, though, is multi-tasking. I like to be able to consume music and webpages at the same time. A consumption device that won't let me multi-task is inherently unsuited for my normal day-to-day use.