Terrain polycount suggestions?

I'm experimenting with the idea of large scale terrains in Unity (I like to have a lot of space to run around in), and I don't find that the inbuilt terrain system is very good for this, given that you can't link the terrain tiles and any attempt to build one large landscape turns into a bunch of mismatched seams into which there appears to be very little way of stitching together, which is very unfortunate because the engine could benefit from a feature like that.

Either way, as Mac doesn't run L3DT, which I hear is a popular solution for mass landscape generation, I turned to the option of blender created terrains, but before I go about creating one I want to know if anyone could supply a recommended poly-count for such a thing.

Thanks in advance.

The inbuilt terrain system is infinitely better for large scale terrains than importing mesh terrains from Blender, since that way has no LOD, trees, foliage, or in fact anything useful regarding terrains. For stitching terrains together, use this (available on the Unity Asset Store).