Something to consider is what you’re going to be reading - if you like periodicals and other stuff with lots of colour images, the screen on the iPad is pretty phenomenal. Magazines like Wired and Popular Science (and even PDF’s of other mags I read like Model Airplane News) really pop on the iPad screen and look great.
I haven’t sat down to read a lot of stuff without pictures
, so I don’t know how well the iPad holds up for extended reading sessions with just text. I don’t get eye fatigue on my laptop, so I can’t imagine it would be too much worse with the iPad.