First of all, if you want to try this baby for yourself, go get it here; the installation might take a while because you need .NET Framework 2.0 SDKs and DirectX (which I didn't have on my office computer). And if you can't remember what the hell WorldWide Telescope is, just remember that it was the thing that made Scoble cry. And we love things that make Scoble cry.
On a more serious note, it's Microsoft's latest desktop application which brings you imagery from many ground and space telescopes all over the world (and above it). It lets you explore space through guided tours, or freely, using a zoom-and-pan intereface.
The bad news is that you're going to have to wait a little longer for our impressions, because this thing also requires decent 3D acceleration, which I also don't have on my office computer. In the meantime, you can feast on these admittedly cool screenshots:
