Well, Martin, I rendered it again last night with higher settings (.65 and AA 7), and at bigger size (2200 x 1000 or so), which took 14 hours. Mainly due to the vapour, and the rendering of trees and other details that hide behind the waterfall (it would still be great if the 'hidden' parts wouldn't have to be calculated). To be honest, the higher settings don't boost the underwater detail very much, I still find it too undetailed. Other settings in the water shader didn't help. And even higher detail settings would take me too long for this fun render.
I roughened the water a tad more (it was too smooth directly after such a big fall), and changed the vegetation colours a bit (and added a washed ashore tree trunk). By coincidence, Darthvader, I happended to indeed dense the vapor.
To me the fall looks bigger than 7 foot, I have no problem with it. Perhaps more foam and flying particles would strengthen the height feeling, but I didn't want too much foam, or you wouldn't see it's water anymore. I played with the idea to add another cloud with very low settings, as multiple drops around the base of the fall, but didn't implement it. It'll work though, I tested it.
I also did a partial render with a boat (and renamed it 'End of Journey'), but got rid of it again, it became too concocted.
It's my desktop now, and I consider it finished. Here's a size reduced update. Time to get on.
---Dune