This is exactly my feeling as well. I would take a huge productivity hit without a phone, or without a laptop. I would mostly miss my tablet on plane rides. I would love to see more data on this though, because I wonder if most non-HNers feel the same way.
I'd say of the three losing the laptop would be the worst. I would be unable to do any of my work at all, and the comm functions of the phone could technically be made up by the laptop and a dumb phone.
Laptop: essential like indoor plumbing
Phone: very useful, major time-saver, but could live without
Tablet: nice for reading but dispensable
Tablets are the only endangered class that I see. They occupy an uncanny valley: too small and restrictive for what you do on laptops, too big to be as portable as a smart phone.
