I just upgraded three servers. It took less than 5 minutes.
On each server:
sudo apt-get update sudo apt-get install mssql-server
No more gigabyte downloads (it needed 145Mb), no bewildering and befuddling multi-page installer screens, just two simple commands and the job was done.
On Linux, at least, SQL Server has gone from one of the most complicated installers in the industry to one of the most elegant.
I love it 🙂