So far I haven't figured out a use for tablets, except for one. In car entertainment.
How often does this happen to you? Drive around town, looking for something to eat but can't find anything. I am too cheap to pay for 3G or EDGE so I have to usually do things ahead of time. But what about those situations where your just out of wifi/3g/edge?
3G iPad! Dash mount the bastard and now you have on-the-go internet for $15 a month. On top of that, you can use it for navigation, playing music, watch music videos, hell even play a few games! Of course I'm a freeloader so all these extras are free.