OK, I installed the old Install_Client.msi, and installed the new Install_Client.msi.
All in all, I'd say go for it. Installing the Install_Client.msi, as above should be ok. At worst, you may have to re-install the older Install_Client.
All bets are off if you do a full install.
FIRST IMPRESIONSEssentially, everything worked as it should, with a VERY few visual oddities.
There was a fairly nice speed increase in FPS, but nothing spectacular.
Wind drift, and turbulence, is much more noticeable.
Clarity of cockpit instruments is back.
There's something that I can't pin down, but "flying" in Prepar3d seems better in some way.
The only negative that I saw was on the surface of sea. And even then, it wasn't always there.
Oh, yes.... Make sure to recalibrate your controllers.