I have used the S80 for 4-5 years. I installed it as soon as it was released.

I like completely redundant systems.
I have my Winter vario on the total energy system with flask.
I have the S80 on electronic compensation. Works perfectly.
It took some minor fine tuning of the compensation to get the two varios to display essentially the same information at the same time.
I fly off of the S80.
My battery died on one long cold flight and it was wonderful to have the mechanical vario system as an independent and dependable system.