"Firstly, let we warn you that the REX bumpmap file to make grass look grainy will make GEX textures grainy too, everywhere, including snow. If all you are using is a REX grass texture and have not installed their detail1.bmp which changes the grain on all ground scenery then what you have is fine. But do be aware that roads, snow, everything on the ground will become as grainy as the REX grass" - Nick Needham"
I have used this detail1.bmp replacement file in the past. It definitely makes the grass look better, as D says, but I was rather bothered flying over the roads and other such things and seeing the same texturing. I guess it depends what one wants to emphasize in their sim. Certainly go ahead and try it out, but make darn sure to back up that detail1.bmp just in case you are bothered by some of its side effects
It goes without saying that backing up the supplied file from REX is advisable. REX suggests that as well in their readme. Your result might vary from mine but I find nothing unusual at all about the look of the snow. To my eye anyway, the snow actually looks MORE realistic with the texture showing a carpet of grass underneath the white.
I noticed nothing unusual on the roads in my system.
As with all suggestions offered like this. Pass on it if not interested or try it using sound backup practice.
If it's not your cup of tea, try the coffee.