hey nice pano shots, just a nitpick, in your '2. Feeble attempt at pano.' shot, right in the middle, the water ripples don't match, can see a rather obvious merge line, you might want to manually clone/merge that area together. =)
Tks saraluna, I'm not sure of the price. I used rectangle filter from Tianya for these shots.
I would think a rectangle Grad ND is way more versatile than a round one.