Implementing normal mapping really helped the appearance of the terrain - they can push the effective resolution of the terrains up by a factor of at least 16 or so. The screen shot this time is from a demo that runs at 60 fps on my laptop, unlike the previous one (which ran at ~10 fps on my laptop).

In addition, I've found that Voronoi noise (aka Worley noise) makes a very compelling basis function for the terrain!