I have a black lumia 920 from EE UK coded (decoded by IMEI code to make it unlocked) I flashed it second times with Amber using Product Support for Store - Nokia Care Suite, once with a french Amber and now with Vodafone Romania Amber - after pressing the Update button I got an warning telling me that I'm flashing a different product code firmware, but let me go on with the update. I think I lost my warranty, but I don't have it, so...

everything went smooth with both firmware...all the software coming with Amber update are onboard, even Data Sense, FM Radio (under Music), Glance Screen (clock on sleep screen and double tap to wake it up etc.).
I got only one problem and I think it's hardware related, because even using the latest firmware from Nokia (Amber) my phone goes to "No Service" status like before the update, so I thought that this update would fix it, but it doesn't...