The sky looks great. But, I think the sky is just very slightly overdone...mostly where it gets bright yellow.
As for the silhouette trees, I think it is a bit boring in this case. I like the outline of the trees, and the cropping that Kal did is an improvement, but I would like to see a bit of dark detail in the foreground. When you have a silhouette that bisects the image, the subject matter is that line. So, the tension or interest is focused in one area in the center of the image. All of the area above and below is kind of wasted. In my opinion, silhouettes that really work have more negative space in and around the silhouette (like seeing tree trunks silhouetted against a sky). If you were going to stick with this version, I might try cropping like Kal did, or even more, and possibly straightening the line of trees so that the silhouette only takes the very bottom of the image and allows the viewer to focus on that FANTASTIC sky.
How about this crop[attachment=3414:attachment]
Even as I look at the crop, I realize that the left half of the silhouette of the trees is kind of boring. hmmm...what to do?