The effect of a newly sharpened ski is noticeable immediately even if you're an absolute beginner. Even moreso if you're on a snowboard.
Source: 30 years of skiing and snowboarding.
The difference is quite pronounced.
I agree with the quoted skier in the post, tuning skis doesn’t matter. I am someone who puts 400+ days on one pair of skis before replacing them, I ski pretty rough terrain and hit my share of rocks, I’ve gotten maybe 3 ski tuneups in my life, I couldn’t tell the difference after any of them. The only things I did to care for them was to store them dry and wax them once per season.
In my experience true ice isn’t that bad in terms of grip, it’s rarely so smooth that edges can’t easily grip on surface imperfections. It’s not fun to ski because it’s very high impact.
I think what most people talk about as icy and slippery that seems to form on skied off groomers is actually some kind of crust that is hard to get edge hold in because the snow is somehow very firm but not well bonded to itself either, so what little edge penetration you get just scrapes off easily and doesn’t support the ski. When I try to picture what is going on in such snow, edge sharpness doesn’t matter, you might penetrate marginally deeper but that just means you’re scraping marginally more snow off.
Edges matter on ice. And yes, the difference is noticable (if the edga has been blunt "enough").
Recreationally, if you are on a narrow groomer type ski on icy runs, every few days is great and will help you enjoy and improve faster. Well fitted ski boots are more critical though.
HOWEVER 99% of the skiers on a mountain (and yes I mean 99%) do not actually ski on their edges, they do skidded turns (https://www.youtube.com/watch?v=S4hioJ4ThJA). And the same 99% will typically just slide off of hard and icy parts of a slope as they aren't comfortably riding their edge. To these people sharp edges matter, but less than to the few who successfully carve.
But if you are within that 1% of skiers that do ski mostly on the edge, then a sharp edge is extremely important; you see true carving technique is a delicate skill:
In order to carve properly you need to need to get your skis in a steep angle with the snow, which means you need to get your feet in a steep angle, which can only be maintained if you move your center of gravity into a position that isn't above your feet. Which effectively means your body is in a position that is out of balance. Similarly to how sprinting essentially is just leaning forwards and playing "catch up" with our legs, carving technique tries to do the same. Exception being that we use the rhythmical centripetal forces of turns and the resistance of the snow to create the balancing force (https://d3t7modobimpp4.cloudfront.net/uploads/_1200xAUTO_fit...).
And this is why edges matter; because if the centripetal force provided from the carving turn isn't generated because the skis blunt edges cause them to slip, then instead of generating movement towards the skiers body (reestablishing balance), the skis will drift away from the skiers body (removing balance) resulting in poor turns if not slipping down onto ones hip.
TL;DR: Very good skiers NEED sharp edges to ski well. Most skiers will be fine. (As a matter of fact I think 99% of all skiers will do just fine on ANY ski, and make more significant improvement from 2 days of ski school than any equipment upgrade or tuning that money can buy).
You could teach a beginner how to carve on a very flat slope though. The 99 percent that slide are just on too steep of a slope for their carving ability. Which is fine by the way. It's fun to go down steeper runs, even if you arent carving.
In which country? I thought carving was relatively popular with locals in the Alps (Switzerland, Austria, etc). At least it looks like that's what they're doing to me, but maybe they still do it wrong.
So what people do is instead of carving perfectly, they deliberately slip to create some friction and slow themselves down.
As an amateur alpine tourist who is deathly afraid of that feeling of "loss of control" from incredible downhill speeds, this is exactly what I do.
That said, I'm here reading because I want to know if the heuristic for sharpening changes when A) one is mostly off-piste (rock, hard ice, etc) and B) really want those edges sharp for ungroomed (ie, icy) slopes.
The truth is that carving technique is just very difficult and more importantly counter intuitive and thus people simply do not learn it on their own as they stop doing ski lessons once they can skid steer, as to many they think this is the same as carving.
After all, it's not like a knife trying to cut through a piece of meat