If I want to do some writing or image editing, using the tablet is a pain, and sometimes plain impossible for what I need to achieve.

I also often download movies and connect my laptop to the TV to watch them. This isn't possible with my tablet, nor is transferring that movie to a flash drive (this might be possible with SOME tablets, but none of the popular ones iPad/Kindle Fire/Nook Tablet).

I use my tablet to browse the internet in bed, read books, play some games, IM and watch videos. I get good use of it, but I couldn't imagine it being my primary computer.