I launched a new addon in the market. It's called Mirage and it lets you generate terrrains and distribute trees over it easily. It also has some vertex groups utilities (so you can tweak the terrains easily).
I'm looking to develop it into a full suite of tools for nature scenes, with automatic materials, rock generation, biomes, rivers, etc.
There's a 50% discount for the first 12 hours to celebreate the launch. The discount will last until 1:30 GMT. Get it while it's hot!
Get Mirage in the BlenderMarket