1. There is no Windows shell, with minimal GUI
2. There is limited managed code support
3. There is limited MSI support (unattended mode only).
4. ASP.NET is not supported (MS is working on the next release of server core to support asp.net)
The tools on server core are primarily designed to be managed remotely e.g. you can manage server core IIS in two different ways:
1. Use the command prompt on server core
2. Logon remotely and manage the IIS using the GUI on a remote machine
Since server core is minimal on GUI and high on functionality side, it is best suited for production systems. You can find more information on Server Core here.