Cloud overcast cover is really bad.
For one, the lighting makes everything fade into the greyness (and me being color blind and only using white icons for enemy becomes even worse).
Then its the FPS issues.I have a GF4 128 now with an AMD1.4ghz 512 ram and sometimes the fps does drop dramatically in short burps, i dont even wanna think how its like for others.
So i would say, change the overcast for the "puff" overcast cloud cover. Much more immersive in my opinion, less fps issues and gives view of groundside to buffs.