I'm not the first to share this, but it has taken me hours to find it a second time, and thought you'd all like a shot at it.
LOGOS prefers to sell you a minimal upgrade/crossgrade package to "really see it shine."
Okay, for the rest of us... Here is the free engine to use what you already have:
http://downloads.logos.com/LBS4/LDLS4Installer/Logos4Setup.exe
After loading, at first you will have access to like, maybe, NOTHING on the new LOGOS 4.0 engine
(you can still use your old 3.0, though). Then the thing scans your computer, starts pulling a download or converting your existing files, not sure.