grind quality suffers slightly when single-dosing

If one always grinds that way and adjusts the grind accordingly then there should be as much consistency with single doses as with an always full hopper.

Also, when switching from caf to decaf, you'll want to sacrificially grind a bit of decaf to purge the last bit of caf out. Retention on the Vario isn't much, but pulsing the empty grinder does not purge it completely, I find.

I find with single dosing that sometimes a bean or bean fragment hangs out above the burrs. A light tap on the side of the grinder gets that last bit through the burrs. (Baratza may not have had a high priority on testing with single doses so may not have designed the hopper to be foolproof in feeding that last drop through when almost empty.) And the chute below the burrs sometimes retains some crumbs that can be tapped out easily to clean the path completely between doses. When I first started with the Vario I used to brush between doses like one must do on the Mazzer Mini but I never got any more grinds out that way, so I no longer bother. But just in case, I always make my wife's decaf shot before my reg shot so I can feel completely guilt free if she has trouble sleeping at night.

Just curious, and a little off topic, but would a bit of "left-over grinds" really have a decidedly (negative) effect on both the taste and caffeine content for the next grind?

yeah, even on the vario which holds very little in the chute.. If I just walked up and pulled a shot, no purging at all.. i could taste the bitterness added from the stale coffee.

i programmed the 'filter' button for 1.5seconds, and i would use that to purge the grinder before a session, and while changing grind settings. i was pushing it twice for the purge.

i didnt notice a grind quality issue with a single dose on the vario... but it works better with a hopper somewhat full of beans. Put 17grams in, and you get like 15ish out. Stick a brush up into the chute, twist, twirl and poke and the extra comes out. using the hopper and the timer, once the system is full, your doses stay consistent.