If I buy one while at WDW (using an American address) and download books when I go to visit in the US
Based on my research on the subject (since I haven't got one myself yet) there's a few problems that will need to be worked out. The logistics are why I haven't taken the plunge myself, although I know someone who has one, since she has relatives in the US who handled it all for her.
It's not just the shipping address that has to be in the US. They will only sell Kindles and books to you if you pay with a US credit card...as in, the card has to have a US billing address.
Now, a couple of the articles I've read suggest getting around that by buying Amazon.com gift cards with your Cdn credit card, then using the gift cards to pay for the Kindle and books. Again, I haven't tried it myself, but the articles claim it works.
If you're getting the Kindle delivered to the hotel, you'd have to figure out availability and delivery times, and maybe order it either before you go or as soon as you get there, to guarantee that it gets to you before you leave the hotel. Sometimes, mail doesn't get to a WDW hotel room as fast as it would get to a residence, since there may be extra sorting stations that handle all the WDW mail. Not sure, but it's something you might want to look into.
As for the iPhone/iPod app, you need to have a US iTunes account. Just because you are in the US, it doesn't mean you get to access the US list of apps. You'll have to either install a new (fresh) copy of iTunes on a computer that doesn't have it and set your account information to a US address, or go in and change your iTunes account info to a US address AND delete your credit card.
As with
Amazon, you can't use a Cdn credit card with the US iTunes (we tried). This means you can only buy the free apps unless you go the gift card route again. I think what you'd have to do is buy iTunes gift cards either in an electronics store, etc. or get an online gift certificate with your Cdn account and "gift it" to your US alter ego.
You can only download books while you're in the US. The Kindle and the Kindle app both still work in Canada, you just can't download books while you are physically located in Canada. So, you'd have to buy and download everything you wanted while you were still in the States, so make sure you buy enough Amazon gift certificates to cover the expected costs.
If it seems like too much effort, I can highly recommend the Stanza app. That's the route I've taken until they figure out the Kindle cross-border difficulties. It's a really good reader, and will read eBooks in quite a few different formats. The info about Stanza is here:
www.lexcycle.com/ and it's easily purchased via iTunes with a Cdn account.
If you do get a Kindle while you're at WDW, please post back here and let me know how it worked out.