There are so many articles on Windows 8 client and its new Metro interface that Windows Server 8 passed by basically unnoticed, except from few IT PRO user reviews.
Of course, first thing that you will notice is that server version is available only through MSDN subscription, also you will notice that it also uses Metro interface. I will not talk about Metro interface since I think that it should be used only on touch enabled laptops or tablets and should not be used on server product. I will rather mention couple of important new features and improvements that Microsoft implemented in this version of its server OS.
Hyper-V is one of the services that got many improvements over previous versions. Now we have new virtual switch that can be configured and modified by third party apps, new virtual machine disk format, VHDX, that can be as large as 16 TB, more processors and RAM in guest virtual machines, VMs can now reside on file shares and can be replicated (Hyper-V replica), so there is no more need for SAN, we can now create 63 node Hype-V clusters that can contain up to 4000 VMs and also we can Live Migrate multiple VMs at the same time over any type of connection.
Active Directory is now aware that it is virtualized and it can make use of Hyper-V snapshots without corrupting AD database. Active Directory Administration Center console is also improved. Now it contains history of all action we did in it and it shows them as PowerShell scripts,also, Recycle Bin feature is now available through GUI of ADAC console. Key Management Server in now incorporated in AD for all OSs that support it (Windows 8 and above). One of the coolest thing that are now more exposed is a new way of assigning permissions to NTFS resources. Microsoft decided to utilize tags attribute of NTFS objects and built in attributes of user account in AD to create policy based solution that can assign permissions to those objects. So, when Windows Server 8 is RTM, you will be able to use common expression to define permissions. You will be able to create policies that will be more compliant with security policies of your company. For example, you could create policy: Only board members can read and modify documents that are tagged as sensitive or top secret. Funny thing is that these tags and attributes are embedded in server OS since version 2000.
Of course, there are obvious changes to Server Manager console, which is now oriented on scenario based management and on managing multiple servers at one. Old consoles are still here, but most of the work is expected to be done through PowerShell which now counts over 2300 comnadlets. Core installation is also slightly modified, in a way that now you can turn GUI on or off, depending on how complex is a task that you have to accomplish.
I am currently testing server version in Hyper-V, and I will also try to get one physical machine to test it directly on hardware. I will report my findings if anything interesting pops up.
There are numerous improvements in file services, network subsystem and protocols that are used. There are over 300 improvements in the OS itself besides Metro UI, that are rarely discussed but deserver more attention. I sincerely hope that Metro UI will remain an option, at least in server OS and that we will be able to chose which UI to use. For more info on what is new in Windows Server 8 please check this TechNet link.