The stream tiles are welcome, but seem like a poor substitute for the fixes that are really needed in the editor - mainly the ability to get water flowing on more than one contour level. At present, water exists only on a single level. In reality, water flows downhill - that is what a river is! The movement of water from one elevation to the next. So currently, if you had two lakes whose water surface should be at say 120m over sea level, and another a kilometre away at 140m above sea level, the one on higher ground automatically sinks to the same level as the first, with 20 metre banks.
The streams are welcome, but much more work to be done as far as the editor goes - building streams is almost as labour intensive and frustrating as the highway sections. The latter are particularly bad since the UI and the small thumbnails don't give an intuitive sense of how the pieces fit together for the most aesthetically pleasing final result.
