MediumRoastSteam Fair point - however, other than in the water tank, everything else in a coffee machine also gets heated to near-boiling point (or well over it) before ending in our cups…
Anecdotally, after 4 months of Zerowater use, the only smell I have perceived is when the filter runs out, then it starts smelling (not strongly, but clearly perceivable - acrid, sharp; not sure if it is by design or just chemical chance). The water tank in both machines is clean and has no smell whatsoever - so far, I rinse them every 2 weeks or so, largely when I remember!
I (like you) think distillation is safer, from a microbiological point of view. However, it seems to me that the risk of a room-temperature filter (be it ion-stripping, RO or anything else) is easily manageable. Eating the ‘decorative’ lettuce leaf from a restaurant has a much higher chance of something going wrong (don’t ask me how I know…)