Thanks a lot for putting in valuable information. The advantages appear to be
Being able to cruise at motorway speeds.
Advantage in offroading.
And of course saving an arm and a leg, very useful while caught in traffic.
The disadvantages seem to be
Finding a mechanically sound auto gear.
The biggest advantage to me is being able to cruise at 120 without damaging the engine. I have driven on motorway innumerable times without any problems but I take care not to keep the rpm above 3000 for long periods.