They have been lately adding features to the services on a regular basis. Every two weeks, they are adding functionality to Azure DevOps Services to match it with what Azure DevOps Server or on-prem would offer. So, we continue to get more robust functionality.
My favorite right now is that they are starting to open up the API availability within Azure DevOps Services.
Another thing that I like about Azure DevOps is that you can use it with any of the products that are on the market. You can integrate it with Jenkins and other open-source products to complete that fully functional CI, CD, CT, CM, and CS pipeline. It continues to enhance.