Server Manager has a new Office 365-esque look.
However, at this point there are still a lot of separate tools with their own interface styles. You still manage Group Policy and DHCP through Microsoft Management Console interfaces, IIS has its own interface with task panes and Active Directory Admin Center is also a separate tool. AD Admin Center does have excellent tools like a graphical view of the AD Recycle Bin for handling tombstone recovery and a PowerShell History. We expect these interface issues to improve significantly by launch.
Those are good ways to teach yourself PowerShell and you'll want to. There are around 300 new features in Windows Server 8, but there are more than 2,300 PowerShell commandlets (ten times more than it has now) adding support for a lot of existing features and indicating that PowerShell is the real management tool for Windows Server. PowerShell is also comprehensive, letting you manage both IIS 8 and Hyper-V as well. Server Manager is really just a graphical way to run PowerShell, which is more an automation engine than a shell, especially now you can use WMI in PowerShell commandlets and create scheduled tasks.
Intellisense and Autocomplete in the PowerShell ISE.
The PowerShell interface has been significantly improved to make the transition easier. Intellisense helps autocomplete commands and paths, there are outlines to help you organise long scripts and inline errors are flagged to warn you as you go along. It's still challenging for less experienced administrators though.
