A tablet or PDA with Wifi capabilities could improve your life even without a data plan, depending on your usual surroundings. A good one will support e-readers and probably the Anki mobile app (I have benefited from the ability to study anywhere), and probably other software to help organize your life. If you don't see this kind of device being useful and you don't come up with something else that you think will be more useful, consider arranging to buy a prize someone you know wants. The loss-aversion bias may make you reluctant to part with your prize, but you may get more utility out of money that can be used elsewhere than out of anything Best Buy sells.
Thanks for the suggestion.
ETA: Back from travelling and re-reading the comments. What makes your more likely to "study anywhere" with the tablet vs. a laptop? Just the lower weight and ~1/3 (or even less) of the thickness? I spend most of my awake time at work, have a macbook which isn't too bulky, but don't take it many places. Do you find that you're more likely to take a tablet and make some small chunk of waiting time useful when you wouldn't have done the same thing with a laptop?
I found out I won second place in an idea contest at work and am being granted ~$400 to spend at Best Buy (the web site for any unfamiliar). Originally, I believe the second place prize was going to be an iPad, but it looks like they've decided to just allow me to pick something in that ballpark price range.
I suspect there are a fair amount of tech saavy folks on LW and thought I'd inquire as to whether you've purchased a device or accessory (or anything from Best Buy-ish stores) that has brought you an increase in efficiency, usefulness, pleasure, etc. The idea of a tablet appeals to me, but I'm not entirely sure what I'd do with it. Also, a data plan is not in my budget, so many typical uses are not applicable in my case.
Anyway, just hoping to probe some collective knowledge about this decision. I'm not very knowledgeable on devices and/or how longer term usage/satisfaction matches expectations or even money spent.
Thanks for any assistance!