Sorry for the slow response, things have been a little crazy this last week.
In the beginning, we certainly found that the lowest bandwidth codecs were ideal if not essential most days. We have since been able to secure a better satellite connection and have a 4Mbps link now which can support the G.711 without too much issue as long as the sky is clear.
In response to a few comments on the thread so far. While a connection to an OBi back in the states does work pretty well, there are really quite few POTS lines still around. Even more, they often would cost more for some form of an unlimited service than a VoIP provider would charge. Additionally, you are in a way adding an extra leg to the connection by putting an additional OBi in as a relay to your final destination. We are already at about 800ms lag with the link as it is, so keeping additional lag down is a good thing.
As for using Google Voice, we have looked at that, and for some reason while I was able to use that solution on an OBi at home, it is no where as reliable or clear as our Vitelity connection has been. As for why this is occurring I wish I knew, but choppy and hard to understand calls make for unhappy families.
Please let me know if there are any other questions.
--PortableTech