Windows Server 2008 received some really nice enhancements since pre-release betas. For example, there's Server Core. It has a command-line interface, a lighter footprint, and a smaller attack surface. It has read-only domain controllers, not unlike the NT 4.0 BDC (Backup Domain Controller) concept, but with a solid purpose of remote branch office domain controller deployment and without the security risk that a writable domain controller poses. There's also RemoteApp Terminal Services. Why "TS" the whole desktop when an application is all your user needs?
And R2 is being developed in tandem with Windows 7, so the two will work better together. In fact, certain Windows 7 features like Branch Cache and Direct Access will require R2 functionality. Group Policy settings for Windows 7 will be enhanced with R2 as well.