Here's a problem you can probably recognize from many games -- obvious tiling effects on terrain textures. The textures look good up close, but in the distance it's obvious that it's just the same image repeating over and over again.
The easiest way to fix the tiling problem is to just fade out the detail maps as they get farther away. Now you never see them from far enough away for the tiling to be visible! The only downside is that distant terrain loses a bit of material definition (it's harder to perceive how it would feel if you touched it), but a little blurriness is much less jarring to me than obvious tiling. Here's the same picture with fading enabled.
This technique works well, but it's not completely satisfying. Can you think of a better solution to this problem?