Yeah, all of us found it rather odd after the beta program ended. We figured there would be a surprise at the end of the tunnel, but it never came. 😀
I've also heard from people in the Windows division that another reason why the boot screen was left blank was because the original plan was to have a full color screen (unlike the XP one), but differences in system configurations (video card models, SLI/Crossfire or not, etc.) made it difficult for them to implement a single way to make this work on all systems. So instead, the boot screen was left blank, and we got a nicer splash screen of sorts (the one with the glowing orb) before the Welcome screen, because that's when the video card drivers are fully loaded, and the behavior becomes more predictable.
And yes, tests showed that it made the boot process faster by a few seconds, especially on older machines, so that was another reason.