Hey jordboss - I think both the Kindle and ID L are great things to have: one for play and one for education. It's a good balance! As far as choosing, it's really where your priorities stand. While the ID L is my absolute favourite Tamagotchi (besides the P1/P2), they will only grow in value and may someday be hard to come by. Consider it a collector's investment. Kindle's and e-readers alike are increasingly becoming more popular therefore resulting in a more affordable product. Like any piece of mainstream technology, the more popular the demand it has, the lower the price tag. I think we will soon be seeing e-readers at the checkout line in BestBuys, FutureShops and electronic stores across the globe in the next few years. I remember when LCD computer monitors and TVs were a "big deal", the technology is so mass produced that it's become a standard for pretty much all TVs and computer monitors at a relatively affordable price. I can see e-readers taking this route.
It's really about perspective: can you wait on the Kindle? Is it something you really want? Same with the ID L, does the cost justify how badly you want it? Prices on the ID L are more likely to go up compared to a Kindle or e-reader - something to keep in mind.
I get equal amount of use from both my e-reader and ID L. The ID L has so many fun features from the decorating choices and pets to the characters and the relatively low key ease of caring. I adore the ID L and I'm sure if you snoop around TT a little, you'll see that many other users do as well. I love my e-reader just the same (an iPad 2). I love the slim profile, the ability to store literally hundreds if not thousands of books on it - and I can take it wherever I go. Kindle's have that amazing e-ink screen which I'm just blown away by. The portability and slim profiles of e-readers are just incredible, it's definitely the way of the future for books IMO.
I hope this helps you make a decision. Most importantly, have fun spending it on something that you really want. Both the Kindle and ID L are amazing things to have!