There are a variety of issues involved in localization. Some are as mundane as the symbol you use for money. Others are more annoying such as the order for a date. For example: 01/02/03 could be January 2, 2003 in the U.S., or February 1, 2003 in France, or perhaps February 3, 2001 in Korea.
Aside from these differences there are also serious content issues. Different locales use different fonts and have their associated FontIssues. Different locales also use different CharacterSetEncodings. Interoperability with these is a must for GE to be useable worldwide. This is also an opportunity to distinguish GE, in my opinion.
Once once has dealt with all of these details, one can tackle the perhaps more difficult problem of LanguageTranslation. And also the general problem of InputMethods.
The YellowTab project has dealt with localization issues in some depth. They are rumored to have a nice NewInstaller that handles the setup for some of these issues.
There is a way to begin with localization without too much difficulty or API changes. This is by using a mechanism of LocalizedDefaults.
