Well, will wonders never cease! While perusing the KB articles today (Zzzzzzzz...) I noticed an interesting article entitled "Write operations to an external storage device take a long time to complete". The gist of the article is that Microsoft has finally gotten around to eliminating the duplicate write operations that file systems developers sometimes see.
The problem is due to the fact that the Modified Page Writer, Mapped Page Writer, and Lazy Writer didn't attempt to synchronize their lists of pages to be written. I first saw this problem many years ago, and when I discussed it with a dev team member I remember being told "yeah, that's just the way it works." No big deal.
Now that there's a proliferation of slow external devices (like, USB key drives and such) this decision has apparently been rethought.
The KB article can be found at http://support.microsoft.com/default.aspx?scid=kb;EN-US;828012 and a hotfix is available.
BTW, this KB article applies to XP Home SP1, XP SP1, and XP 64-bit Version 2002 SP1.
Good news is welcome, no matter WHEN it comes! Hooray!