Basically the image is exposed one stop more than ISO 200 and the data shifted over to reflect that. You get the same results shooting RAW by using ISO 200 and increasing EV by one stop and then readjusting the data in the RAW converter by setting it back one stop. For instance, if you are shooting at ISO 200, 250s, f/8; then you could just shoot at ISO 200, 125s, f/8 and without switching to ISO Lo 1. Using ISO Lo settings on the D300 are helpful if you are shooting JPEG, using Speedlights or studio lights and want to use a faster flash sync speed instead of stopping down the lens or reducing the output of the strobes.
I like shooting long time exposure,
and most of the time I do it on ISO 200
I try not to go up or down, since I did not
Understand what was happening at Lo 1,
but will try what you are saying and see what