Hi Markus. Yes, it might be missing some features, but so is Azure SQL Database and SQL Server via Amazon RDS. But not everybody needs all of those features and enough people can make use of this to have indirect benefit to the community in general.
Understandable that you prefer a GUI over command prompt, but they might have an emulator that allows SSMS to work. It has been 17 years since I have played with it, but there used to be a "wine" project that emulated windows on Linux. But more importantly, the point I was making is that we ourselves don't need to be the ones directly using the Linux version of SQL Server to benefit from its existence. As long as enough other people do, then that will provide indirect benefits to people who might never touch Linux or SQL Server on Linux.
Also, the cost difference between Linux and Windows isn't much at the very small scale. But as the number of VMs increases it really does make a difference. This month's presentation at my local PASS chapter, TriPASS, was about running SQL Server at Amazon, both as RDS and on an EC2 instance. One of the things that the presenter mentioned was the large cost difference between Linux and Windows EC2 instances for large scale projects. So this will certainly be a decision factor for some companies.