I was using ultrasonic scalpels back in 2002. They were smaller than this knife.

My first job was at a knife shop so I’ve seen everything from stamped steel fantasy nonsense to traditional style hand forged items. There’s a lot that goes into making a good knife and you don’t need to spend a lot to get one. Similarly you can spend a lot of money for marginal to no benefit.

In general a hard edge with a softer back is necessary for a strong knife that will cut well. This is a function of heat treatment. A knife that is tempered the same the whole blade is fine for smaller knives but it’s possible to break the tips or edges off larger knives. From there metallurgy affects the edge retention and how easy it is to sharpen. Plain 440C will make a fine enough knife if heat treated properly but can also make blades that can’t be made particularly sharp and can’t easily be sharpened. These knives will be very stainless so this is why poor quality and good quality knives will be made in 440C. The next tier of knives beyond singular steel forging will be a very hard edge steel wrapped around a softer core steel. The sky is the limit from there in terms of metallurgy. The highest end knives will use powdered steel where precisely composed steel bars are made using uniform grains of steel and other attractive metals and doping materials as part of the forging process.

Once it gets home a good edge has to be maintained.

People do all sorts of things to dull perfectly good cutlery (I cringe when I see people use glass or marble serving/cheese boards as a cutting board). A off hand toss of a knife into a sink can roll the edge.

The worst offense is when I see someone at a farmers market with the grinding wheel “sharpening” a knife by crudely removing the hardened steel edge of a knife. Good luck cutting much with the softer core steel or softer tempered back steel.

While having an Evangelion style ultrasonic knife is cool, it’s certainly not necessary and I expect it can be ruined in many of the same ways a $400 traditional knife can be.

At home I have Henkels for the holidays and some forged food service knife’s for general use. When visitors throw the food service knives into the sink I just take out the sharpening stones and don’t cry all that much.

I'd try one out of professional/academic curiosity (I'm a chef), but am highly skeptical of this product. It looks like absolute trash.

All the people saying this knife does anything remarkable clearly have no experience in maintaining a decent knife blade. I've got knives that I've had for over 20 years that perform as well as this thing appears to (in the slick prepared advertisement).

Having said all that, you won't find an accurate takedown of a product that isn't on the market yet. Still, I can't help but wonder if the person behind this had dedicated that effort towards helping mitigate the water crisis, deforestation, or any number of other inarguably nobler pursuits.

(and yes the Japanese steel dulls too. No cheating physics.)

Higher HRC would retain the sharp edge for longer, of course - but again much harder (literally) to sharp them.

I tried a compatible strop that clicks in but it's not worth it imo; just use a normal strop.

When it does come time to sharpen, I constantly see places offering knife sharpening services, and they’re usually cheap enough. Or you could get a gizmo that does a mediocre job (and shaves away far too much material) if you just want to get it done. Or you could learn to do it yourself which isn’t that hard or time-consuming but is somewhat of a labor of love.

Learning to sharpen the (correct) knife (for the task) will do as much or more for the chef who struggles here.

Prepping 1000 lemons? An ultrasonic knife is not your answer.