Floating post-post-apocalyptic islands???
No, but really, you're taking "reflective water" to a lever where it really just doesn't look natural, this terrain's mirror-water looks more like it's a part of the sky than it looks like glass-like water, I'd suggest removing the reflections, but if you can't be swayed, I guess I suggest you put out some (more) water planes over the reflections, to make it more like... Well, water.
And, if it happens to BE floating islands, my advice still stands, only then it's more in regard to ditch the "floating" part in "floating islands."
Also, those mountains really don't look good, as a rule of thumb, I'd say, never use arching mountains that gets lower on either side of the terrain, while it sure as fuck might happen in a natural setting, it still doesn't look good, screw it up a little, add more mountains and different distances, some behind, some in front, and then fiddle around with the fog to make them meld together nicely, oh and, on the subject of fog...
There's only one aspect of a terrain that ALWAYS has to look 100% natural, at least most of the time. And that's the fog. Where have you honestly ever seen yellow fog like that in real life? If you want to implicate some kind of lighted-by-sun fog feeling, I suggest you tint the fog to a natural colour and use the Glow model to add flare effects and sun-shafts, and while you're at it you might want to add a sun.
- Oh and the "Sun_Flare" model is relatively sexy, just sayin'.
I also suggest a better variation in... All of the flora, the grass looks awfully spammed and the tree models look too repeated, you should mix in some other tree doodads, as well as mix up the underbrush by using flowers, rocks and other bushy things. I would suggest you use another tree model altogether, cause I find that model to only look good on rare occasions, when used correctly, but then that's your liberty to use whatever doodad you want.
Oh, and, really! And this actually goes out to all Terrainers it concerns: Use F, K and G when you screenshot, not just "V"... and if you really can't bother doing that, cut the damned red text at the top.