I am currently using REX Essential Plus and I love it- but I have been looking at REX 4 recently and I was wondering if I could get some input as to if it's worth the cost or not. The screenshots look great, but will I really see that much of a difference within FSX? Thank you.

 

 

You bet, its a no brainer, clouds are more realistic, as well as runways even look better, Truthfully take fsx into a new direction, I also had rex essential plus, my flight simming is even more real with this new addon.!!!

Is there an upgrade option then, or is it a fresh install of a whole new product?

Yes an UPGRADE Option would be excellent!

For me, textures are a little better but not much, plus there are some that work better w/ P3D V2.x, but the big selling point is the ability to load a whole theme of new textures in a virtual instant.   And the usual cadre of community developed themes is present.   I think this helps offset becoming bored w/ the same set of textures.  There are some downsides though for me:  it's not possible to do any editing on the brightness of water textures by directly tweaking them.   Also, I don't like the interface in some ways as much as in REX E+.   It's not easy to quickly see which exact textures are loaded at any one time.  In fact, it doesn't seem to show what the current theme that is loaded is...does it anyone?