#1 Some like the look of flowing water over frozen. If you want the flowing look f4 is way too open. Stoping down will help here. And the person in the picture. I would not have noticed if I had not read your post. Although a great concept. Love the double rain bow.
#2 Really nice. Rain covers work for rain. But don't keep the actual lens front dry in those conditions. I would still want one on my gear.
#3 Great shot. Just for kicks try copping out some of the top and left. It may help to bring out the falls a bit better. But this is more of a personal taste issue.
#4 Nice overall shot. Cropping to something like 16:9 may help make the falls stand out better.
#5 I do prefer this shot to #4. Many, many shots could be taken of this area.
#6 Great colors and texture here. Getting closer could help. But getting into a position to show the overall landscape can be a real challenage.