I think the biggest advantge with Butterfly Variometer is that you get actually get several instruments in one package. The "normal" TE-based vario is very good, in my opinion on the level of the best traditional electric varios (Zander etc.). And then you get the netto vario that can be configured to be totally independent of the TE system (though it can be mixed with it), based on inertial sensors. After flying for a while with Butterfly one really sees how important it is to know wheather gust is vertical or horizontal. Traditional TE system can't separate these reliably. Netto variometer and real time wind calculated by the inertial system gives very accurate picture of the airmass around you (and as a side produt most accurate speed-to-fly commands I've seen). In this respect Butterfly Variometer is not comparable with other current systems. I think this fundamental difference is not completely understood here.

krasw