The dev.azure.com URL - can I move away from the old visualstudio.com URL?

Plenty of reasons behind this, but you might want to move away from your <organisation>.visualstudio.com URL and onto the new dev.azure.com/<organisation> URL as a matter of standards.

It is fairly easy to do - straight from the Overview Settings page of the organisation:
















If you configured your Build Agents on-premise with a PAT and the old URL you are covered, the configuration will still work, plan for this in advance anyway and make sure you are prepared 👀