For those who would looking for specific downloads of the PowerPivot for Excel 2010 RTM bits , here they are:
Important : If you install the 32-bit version of Excel 2010, you must use the 32-bit version of PowerPivot. If you install the 64-bit version of Excel 2010, you must use the 64-bit version of PowerPivot.
PowerPivot for Microsoft® Excel X86 Executable (32 bit) (or here: http://go.microsoft.com/fwlink/?LinkId=186058&clcid=0×409)
PowerPivot for Microsoft® Excel X64 Executable (64 bit) (or here: http://go.microsoft.com/fwlink/?LinkId=186059&clcid=0×409)
Enjoy!
[...] notes that PowerPivot for Excel 2010 is now available as a download as well as some great Launch Day testimonials for [...]