Well I am now producing what in my opinion are decent procedural textures for the planetary terrain. They are generated per pixel every frame. This has the advantage of allowing infinite resolution as well as eliminating any texture coordinate warpings around a sphere, since the textures are actually 3D.
As I mentioned before, this does require a significant performance hit. I have managed to simplify the texture generation to the point of having reasonable framerates while maintaining decent texture quality. What I am doing is calculating 4 separate textures using 2 octaves of turbulence noise at different scales for each one. These 4 textures represent sand, grass, rock, and snow. They are then blended together based upon the terrain height to generate a final texture.
I am getting anywhere between 25-50 frames per second depending upon how many pixels of the terrain are taking up the viewport. The average for normal travel is 35 frames per second.
Here are some screenshots of the results.