I would seriously only use a small set of languages to start out. When you submit the app to the store, for every language that you've included in your app, it is going to make you provide all of the descriptions, features and screenshots in that native
language. It will take you forever to do the submission if you include all 100+ languages.
Also, the Multilingual App Toolkit makes this a lot easier. You just have to create your resjson file and the toolkit builds the languages you choose from a list. NOTE: The toolkit download was updated a couple weeks ago to work with the release version
of VS2012, even though the web site still makes it seem like the old preview version.
Hope this helps...
Rob