Some recent and not so recent studies (maybe sparked by anti-iPad propaganda?) are recommending not staring at a laptop/iPad/PSP late at night saying the proximity of the light-emitting screen are throwing off your circadian rhythm and not allowing your body to produce the melatonin it needs for a restful sleep. These studies argue that TVs are somewhat better (since they’re typically further away from you) and that ebook readers like the Kindle/K2/Nook/etc. are even better. Of course, there’s the old-school paper book O_O. I’m not sure if i’m the best candidate for this (rarely get through an entire night uninterrupted anyway) but it sounds fairly reasonable to me.
If you must work (or “work”) on your computer late, it might be worth looking into F.lux – a brilliantly simple program that uses your location (it guesses, but you can give it exact coordinates) to adjust your LCD to appear “warmer” at night so it won’t burn out your eyes. It seems like a really good idea and if you’re just browsing/reading late on your lappy/netbook/etc. and not doing any color-sensitive work, it might just be the thing you’re looking for to allow your body to wind down.