@Ian2: Shouldn't be the case. It all depends on which countries you enabled when you publish. Apps will fall back on the so-called Neutral Language which you can set up.
It can be challenging to localize an app. The UI in VS2010 will only show one language at a time, I would prefer to see a grid so I can better spot any mistakes plus it's easier when you want to add a single term, as you now have to open each resx independently.
That said, feel free to try out my app Weerplaza.nl, it's currently primarily targeted for usage in The Netherlands and shows rain clouds and a 2 hour estimate of rainfall in a live tile. So anyone living in or just visiting The Netherlands should check it out, in the 1.1 update which finally after half a month got through the Marketplace update you can turn off the Radar Live Tile so you could also use it outside the Netherlands and pin your favorite places, although the place name could be in Dutch
Posting from my Dell XPS15 running Windows 8 Pro, VS2012 Ultimate and Office 2013, waiting for the WP7/8 SDK!
Edit: finally after 3 weeks I got thrown off first place in The Netherlands by Whatsapp Actually it's a shame, since Whatsapp has done an awful hack with the background audio!