Nice. May I? I would move the boat its own length to the right, so it doesn't sit on the edge of the island. Also, I would use a softened (0.002) reflective shader for the sea reflection (instead of the reflection of the water shader), so the far reflection is much softer.
And what detail settings would you talk about for a final that would take so long? Depends on the machine of course, but a setup like this should be ready fairly soon (0.6/AA6, soft shadows, I guess 2 hours on an i7 max). Try taking out the compute terrain, you won't need it I'm pretty sure.