The portability is the big factor for me.
I do a lot of reading/research on my tablet for school. I love being able to pull up articles in my school's library database on the tablet instead of a full blown laptop. It is much more comfortable to sit and read with on the couch, deck, coffee, shop, etc...
In addition to being a student, I'm also a Linux sysadmin. I'm on call pretty much 24/7. The tablet keeps me from having to lug my laptop around with me everywhere I go in case my monitoring systems send me alerts. I can fire up my SSH client on my tablet (I use Better Terminal Emulator Pro) and log into my servers from anywhere in the event of some sort of emergency. I also do work email on my tablet when I'm not sitting at my desk.
For non-work and school tasks, I use it a lot for social media and web browsing while sitting on the couch. It beats the heck out of sitting there with a hot laptop on my lap!
As my son gets a little older, we'll use it for interactive storybooks and toddler games too.
I actually have decided to go back to an old school flip-phone for my cell service and use a 3G tablet as my "smart" device. I used to have a Galaxy Nexus and a tablet. Going back to a "dumb phone" has allowed me to unplug more effectively when I want to but still stay connected the way I need to for work. I save money that way too.
-SF