With ice not so much worried about flavor. Water treated though RO has no flavor. Totally flat. One reason I switched from using it (other is the system is a bit of a PIA to keep up and a bit expensive) so switched it over as all the filters and membrane are due for replacement and full system flush and clean. Actually easier and cheaper to buy a new system. But you still get very "flat" tasting water. (nice clear ice) but water tastes flat and I guess the coffee makers recommend against it.
When I bought the water carbonator to make my own sparkling mineral water, I then faced a bit of a crossroad. We have very good Artesian wells here. And knowing folks who have private wells tied into the same aquifer I've tasted the fully (very hard) untreated water. And it's like the expensive spring/mineral water you buy in a specialty shop.
I wanted to mimic the flavor of that Italian (read $$$$) water I was buying as it was REALLY good. So, a little plumbing in the basement, a trip to Menards for a couple T fittings and inline valves, and nice filtration system with easy to replace (push button, twist cartridge 1/4 turn, insert new twist and lock) filtration system
https://www.menards.com/main/plumbi...p-1501223587675-c-1535732895503.htm?exp=false though I did replace one cartridge (the main carbon block) with a better carbon block with this cartridge
https://www.menards.com/main/plumbi...p-1501223587610-c-1535732895503.htm?exp=false Simply because I have read we've had some VOC's in the aquifer (though the issue was localized to a couple small areas around here and supposedly not tied into the entire aquifer). Apparently it only affected those folks who were in specific areas with more shallow wells. In any case I felt like all things considered the extra $30 for the higher end cartridge was worth it.
My efforts were rewarded with wonderful water. Nearly impossible to tell from the high $$$$ stuff.
Only thing is I don't get clear ice from the new fridge.
Now if there was a way for me to run a separate line to only the dual ice maker I actually would take the time to buy and plumb a new RO system to only the ice maker. But it's just not that important to me. I am more concerned with having good tasting water overall.