There still is NOT a publicly-available reference to KB976902 (AKA the Black Hole Update). I wouldn't install it either, at least at this point.
<edit #1>
KB976902 will almost certainly be a Prerequisite Update for Win7 SP1 RTW, just as KB955430 & KB947821 were Prerequisite Updates for Vista SP2.
</edit #1>
<edit #2>
It would appear that KB976902 has been pulled.
</edit #2>
**<edit #3>**See...
Demystifying KB976902, a.k.a. Microsoft’s “Blackhole” Update
http://krebsonsecurity.com/2010/10/demystifying-kb976902-a-k-a-microsofts-blackhole-update/
**</edit #3><edit #4>**KB976902 is now live:
Description of the Windows 7 and Windows Server 2008 R2 installation software feature update
http://support.microsoft.com/kb/976902
According to KB894199, this update was (re)released on 11 January 2011 and is a Prerequisite Update for Win7 (and Windows Server 2008 R2) Service Pack 1 when it is released.
IOW, SP1 will NOT install (or be offered by Windows Update) unless & until KB976902 is installed. So if you've hidden it and it's not been automagically unhidden, you will have to unhide it manually.
• HOW TO Hide an Update or Restore a Hidden Update
http://www.sevenforums.com/tutorials/24376-windows-update-hide-restore-hidden-updates.html
</edit #4>
<edit #5>
Other Win7 SP1 Prerequisite Updates may include KB947821, KB2534366, KB2454826, KB2533552, KB2552343 and/or KB2529073.
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</edit #5>
[Last Revised - 30 December 2011, 19:12 UTC]