Well, It has been a while since I had time to work on the engine, but today I had some time left.
A few days ago a found a tool called L3DT. It's a very cool and capable terrain generator and it inspired me to improve the texturing of the terrain.

Near the camera I use the same splatting technique as before but the textures are tiled at a much higher density so the ground look really highly detailed even if you look straight down. This ofcourse causes ugly repetition patterns further away. To hide this I blend in a large (1024x1024) color texture on terrain far from the camera.

I've also changed from vertex lighting to a normal map. This makes the lighting independent of the LOD and reduces popping artifacts. It also makes the distant terrain look more detailed.

I use L3DT to generate all texture data I need, since it does that a lot better than my own hack;)