I put this into a new topic in order not to SPAM other topics where this question came up.

I thought that a vario needed to use the 3-D inertial sensor to sort out the horizontal and vertical components of "gusts", and I thought that nobody was doing that just yet. Or does the inertial sensor just make the filtering better?

Well, actually a vario is an energy difference indicator. Many people (at least here in europe) want to know if total energy changes, even if the energy addition is due to a gust rather than thermal updraft. The vario needle in Butterfly Vario remains the "energy difference indicator" just as you are used to (inertial sensors are used here to e.g. acceleration induced errors etc..)

We have another indicator (blue round indicator) that indicates vertical airmass movement (kind of a that what was called netto vario in the past, but determined differently). The vertical airmass indicator is based on the inertial reference system and therefore will not show horizontal gust-induced energy changes (this can be mixed with conventional netto and tuned by many factors taking installation etc. into account).

This way you get both. Precise energy difference indication and indication of vertical airmass. Both indicators together give you a good situational overview. You know where the energy change comes from. Knowing if its worth slowing down to thermal or if the energy addition you just experienced is due to a gust is a very cool thing, especially when flying heavy gliders.