Something to consider for those who wear glasses:
I do very little on my iPad beyond reading newspapers and magazines. Most of my actual activity is on my laptop which mainly stays in one room. So I got a pair of computer glasses that I keep next to the laptop.
They are simply reading glasses optimized for the distance between eyes and screen, which in my case is more than arm's length (I use an external monitor instead of the laptop's own screen). It's so nice to have the perfect correction/magnification while using the computer that I probably spend far more time at it than I should.
When I get up from the keyboard, I just lay the computer glasses down again and get on with life. A cheap but very useful gadget.