We use our (really mine, but hey...) Mini 5 for reading PDFs, reading ebooks (when I can't find my kindle), a quick terminal session to my server to check stuff, menus at restaurants for take-out, and really just keep it laying around to look stuff up as we need to (recipes, school schedules, etc.). It's pretty handy to just have it easily accessible.
I use it for reading pdf's. Sometimes for gaming. Sometimes for kindle books, but prefer a kindle for that.
I want to buy one to replace my Moleskine. Drawing, notetaking, etc, but with layers and an undo button.
They seem extremely popular in aviation as well as in cars for off-roading or travel. Cheapest way to get some really great maps.