I find this new behaviour extremely annoying - basically, it forces you to write unnecessarily long winded SQL commands.

I am completely at a loss as to why Microsoft should have seen fit to generate errors where none need exist. I am quite happy to deal with the explicit ambiguity of the 'old style' of group usage.

Surely a better way of implementing the new behaviour would be 'SET SPURIOUSGROUPBYERRORS ON', rather than forcing us to switch it off?