Looks like the "Correct Aspect" switch when using unwrap is completely ignored. Results are always the same. Shouldn't switching it off mean that the whole UV space gets covered, regardless of the aspect ratio of the unwrapped geometry / image?
First of all, a few things to note: Correct Aspect has to do with the ratio of the image, so for square images, it won't have any effect at all. For non square images it accounts for the fact that unwrapping is done to a square target space and actually modifies the UV coordinates by the aspect ratio of the image to avoid any stretching introduced by mapping a square space to a rectangular one.
This looks like it's working like it should on latest trunk. If there's a case where it doesn't could you please post a file/image that fails?
I did some more experiments and i believe i found the issue. The aspect ratio might be stored for the first initial unwrap, but it is not updated for further unwraps on different textures (aspect ratios). I will give an example:
1. You create a texture with 512x512 px (1:1 ratio) and unwrap the mesh. Now the ratio gets stored for the UV-Layer as 1:1.
2. Now you exchange the texture. Either loading a different image (replace) on same slot or change to a different image slot. If this texture has not the same ratio (for example 1024x512 px, which is 2:1) then the aspect option will fail since it still assumes a 1:1 ratio, not updating to the ratio of the currently chosen texture.