The international version will work in "over 100 countries and territories", but Amazon doesn't specify if there are any additional charges for using it in a place other than the one where you bought it. It also looks like AT&T is the one that will be providing overseas roaming coverage for the GSM version. [Amazon]
Update: Ah, here's the bonus price.
Low Book Prices: New York Times Best Sellers and New Releases are $9.99, unless marked otherwise. When traveling abroad, you can download books wirelessly from the Kindle Store or your Archived Items for a fee of $1.99