Differences between Windows Server 2008, SP2, and R2

So what are the differences between win2k8, win2k8 SP2, and win2k8 R2? These naming conventions and differences between versions are a constant cause for confusion. So here's the short take:

Win2k8 was first released with SP1. Later on came Win2k8 SP2.

Win2k8 R2 is the new version of the OS that introduces several new features. It has the look and feel of Win7, it is only x64 bit, and Hyper-V Quick migration (~VMotion) is introduced.

There's no SP2 installed on top of win2k8 R2. R2 is a clean install or you can upgrade from SP2 to R2. In any case, the SP2 will disappear and it will only be called R2.

The reason for pointing this out is that it was a bit different with win2k3. Here, you installed SP2 and then you installed R2 on top of SP2 and the result was win2k3 SP2 R2 - so service pack and R2 at the same time.

I found this comparison somewhere and I quite like it (not quite sure how correct it is, though..)

Windows Vista SP1 ~ Windows Server 2008 SP1

Windows Vista SP2 ~ Windows Server 2008 SP2

Windows 7 ~ Windows Server 2008 R2