Risk fail, screwy tank.
Kidding aside, I do feel that the moving the river in a direction away from the middle of the lay out does draw the eye to the edge of the tank-- which is not good. The eye follows the river, which is bright.
As I said to Kelley, the depth of the river should be improved either by a lower sand level (revealing more of the rock at the river edge) or sloping it (has a similar effect) which I plan on trying after the tank settles a bit. You wouldn't know with the sand covering it, but I had planned some very careful rockwork that's unfortunately been covered up.
As for the "barrier"-- I don't feel that way. This is probably a result of my Hawaii bias. In Hawaii, water always runs from the top of the mountain to the sea-- rivers are like that, but in Hawaii where the whole island is one big mountain, this is especially felt. The movement of waterfalls down the mountain through ridges to feed streams. To me, it feels very natural to have a stream flowing from a mountain. The rocks in this layout are also built with this idea in mind. With a shallower stream, I think this sense will come out stronger. Right now the stream is proportionately "too big"-- much larger than my initial plan. When I take sand out, it should appear much smaller.