I wonder if there's any difference at all vs the grey HPWC other than just the front cover piece.
If it doesn't show up in time for my scheduled installation in the next month or two, I might just buy the grey one, swap the black cover on when it arrives, and eBay the "signature" unit with the used grey cover from the original. Easier than de-installing and re-installing a whole HPWC (which doesn't look that difficult either).
Might lose a few bucks in the process, but.. *shrug*