I found that the clouds to be VERY detailed and accurate however I take a big hit in fps when in detailed clouds are selected. I played around with the other settings and trying to find the best combination. For the price, it's totally worth it.
Keep tweaking until you find some good settings.
There's an option in there somewhere to use DXT3 textures - if it isn't already selected, select it and save your changes. This can make a big difference, as it reduces the file size of the clouds. I'm getting better performance than with the default (i.e. pre X Graphics) clouds.
Are you referring about DXT5? I could not find DXT3.
WHat is the difference between 512X512 and 128X128? Which one should I select?
Sorry, yes, meant DXT5.
The lower the number, the less detail, but the better fps. I'm using 128 and they still look great but perform better than the FSX default clouds.