The iPad's relative uselessness for getting real work done is probably one reason I get so much value out of it. When I'm on my iPad, there's not much I can do but think through, sketch out, and plan my work—whether that's with the Pencil in Notes or organizing my to-do items in Things.

I rarely do these things as diligently on my Mac, because it's so much easier to stick my head in the digital sand and just bury my head in whatever work is right in front of me.

Not exactly a ringing endorsement of iPad, but it is genuinely useful.