Just finished downloading & installing WinFS beta 1 on my XP machine.
Already noticed a couple of things, If u copy a .doc file into the "Default Store" and double click it is opens fine, but if I copy a ".chm" into the "Default Store" and double click it, it opens and just displays the content tree the main content area has a error message, i guessing some security issues.

Update: The following KB link helped me solve this issue http://support.microsoft.com/kb/896054/