erm, the one I have is the cheep classical hard edge gradient. To be honest, I've been looking for this type of filter you described but I never found one. I think it will be reaaallly useful for scenes like this.
Ah and you asked for it on this one. You have some great scenery but you didnt use it to its greatest advantage here. This is mom's "best" snapshot. But it is not up to the level of some of your other stuff.
The focus here should be the tree and the sun, chop off the top part of the sky to just above the tree, leave in all the ground, its your perfect leading line. Then your close, but you centered the sun and tree, set them to the left of the frame and you would have had a real winner, something everyone would want hung on their wall. Keep at it.
Mom doesn't like what I do .. and I can fully agree in here. The Sun was setting and I was fooling around with the tripod looking for the best shot position, but I couldn't find it. Something was always missing. If it was the great sun's position, it wasn't the tree's... or the leading lines was not at the right places. AND a huge sheep dog was barking behind me, trying to break its leash.. so I tried not to move too much.
I have other shots from this sunset and as long as I remember this wasn't my favourite ....