Terrain

What would you guys say would be the best bet for large terrains? possibly continuous. and pretty good detailed. I would use height maps and such, but isn't it harder to make them seamless? also i wouldn't know how to texture them besides one large huge texture. Ive heard of texture splatting but it sounds way over my head. One system i devised was to make the terrain have a couple layers like dirt, road, rock etc and then you would paint by setting the vertex alpha of each layer and optimize so polygons not seen weren't drawn. not sure if this would be a fast/good system