I use my first gen iPad for mainly reading scientific articles. Especially when starting research on a new topic it comes really handy since I hate reading papers on the computer screen and I would hate to print 100+ papers (~1000 pages). Other than that, ipad is my 2.5 yo son's primary entertainment and my wife's email checking and facebooking device :)
I bought an android tablet for under $50 and basically only use it to check my email and notify me be sound, wherever in the house I take it, that I have email in, but only move it around when I expect something the would demand my urgent attention (I don't pay for regular cell phone service)
My tablet was originally purchased to be a replacement for my first gen Nook with a few extras. Now it's like my second attachment. The only downside to it is that it's WiFi only, so I can't use it for things like Navigation. I use it all the time for almost everything else on this list though.