For what its worth, I voted this shot a 7. Its been awhile and I don't remember my impressions at the time, but I can tell you that I think this is an awesome shot. I am a huge fan of landscapes and wide angles (I own the same sigma lense) and to me this really is an underrated photo...
A few of your B&W landscapes caught my eye, but I'm going to start here down in the 5.5 range which allows for a picture that has great promise, but didn't quite make it. The sky in this one, of course, is awesome. I'm guessing you are way down near the 10mm end of your lens. Your processing is well done, although I wonder if you couldn't have tweaked just a bit more contrast out of your lower clouds. The feature that lets you down is not having a foreground or, really, any subject. Some pics can get away with that, or the sky itself is the subject, but here our eye needs something more. This is a potential limitation of shooting so wide. Any subject is going to have to either be really close to you or be really big.
Very well titled! Definitely expansive and lovely in B&W. Do I see windmills in the distance? (Trying to figure what the little white posts are between cloud and ground.)