This morning I upgraded the Where Was Dr. Neil and the Locus Activity Map web pages to use the released version of the Bing Maps Silverlight SDK.
The upgrade from the CTP took under an hour. There are some minor naming differences, for example the VirtualEarth namespace has been replaced by with a Maps namespace. It is now Microsoft.Maps.xxx which makes more sense.
I believe you only have a few more days to perform the upgrade, and then the CTP service will be shut down.
You will need an account key for each web site on which you host the Silverlight map control. You can get your key by creating an account on the Bing Maps Portal.
Then the key needs to be placed in the XAML when you add a Map to your Silverlight app.
The Silverlight interactive SDK is pretty handy to get you started once you have downloaded and installed the SDK.