I don't know about Loader. But I will share my experience with the import (imp or imp80) and export (exp or exp80)
to move whole tables or schemas from version to version.

There is one trick and that is that the versions from database server version to version don't work.
But you can always use the version that you want to import into.

For example if I have Oracle 7.3 and Oracle 8.1.6 and I want to take data from 7.3 to 8.1.6
I need to run exp from the 8.1.6 machine and connect to the 7.3 machine to make a 8.1.6 compatible export file.
then I run imp from the 8.1.6 machine to import this file..

Conversly if I want to get data from the 8.1.6 machine into the 7.3 machine. I run the utilities from the 7.3 machine.

I would guess either Loader is the same or you will have no problems at all.

Hopefully that's a little helpful.