Let's keep this thread focused on PDF Scanning in Windows 7 and not general setup.
I have successfully set up the HP Solution Center in Windows 7 RC and connected to my Officejet Pro L7650 via ethernet, using the option for "Vista" compatibility (i.e. not Vista SP1 or XP). I have scanned documents in using png and gif, but I don't even get the option to scan in pdf format.
This is the only issue that I can see with the Windows 7 installation, there are no other features or functions that I can't access.