On the subject of "it's a feature not a bug" one of the answers I received did follow this line ...

I reported that I thought it was a bad idea to have the technical preview default setup take over all the office file associations as the technical preview is "not for use in a production environment".

The reply I received was that this was "by design"

Now I agree that this is good practice for a RTM/Retail product I still feel it is a little dangerous with a preview product where all the existing documents load with a pre-beta product.