I uploaded a windows phone application on the windows store several months ago. Unfortunately, I've lost my source code (because of an hdd problem)!
Did you guys find any way to download your appx package to try to decompile it ? (From the dev center or the windows store ?)
I could't find any features of this kind on the dev center. It's too bad because it would be very usefull to me in my case.
It's not possible to download it on the dev center at this time. But I contacted the Microsoft support and they sent me the .appx file a day later. Very efficient support !