The only thing I can really suggest is breaking up some of the color detail in the rock; maybe use vertex color and some random perlin noise for variation?
Also, any reason you didn’t use the new lighting model for the grass? With some work, you can get great results. You could also blend the landscape texture with the grass texture via photoshop, using match color, and using the landscape grass texture as the reference. This should allow all of your LOD’s to blend better with the ground.
One more thing - is that water using caustics? Anywho, good job!