What a difference an operating system makes. If you install the new Windows Search 4.0 Preview on Windows Vista, the changes are visually non-existent:
Windows Vista with SP1, before WS 4.0 Preview:
Windows Vista with SP1, after WS 4.0 Preview:
OK, that's a joke, sort of: I'm using the same image in both cases, because Microsoft isn't visually changing anything. The changes are all under the hood.
On Windows XP, however, it's a different story. Before installing WS 4.0 Preview, you get the silly "XP dog" search application. But afterwards, you get something that's very reminiscent of the old MSN Desktop Search tool:
Windows XP, before WS 4.0 Preview:
Windows XP, after WS 4.0 Preview: