I generally avoid taking advantage of any kind of deal like this without doing plenty of research, and found a review on cgchannel

I followed that to the Silo forum on CGTalk.  According to a few threads there, this is the first update for Silo in over 3 years.  The original developers abandoned the program some time ago.  And the Windows version is 32-bit only.

I'm gonna save my $20 and continue learning how to use Blender.