AUS-10 is basically 440C, and is an excellent steel for cutlery (and was once considered at the very high end of stainless steels). Very stainless, reasonably tough, and honorable slicing edge retention if heat treated to a relatively high hardness (60-61HRC would be on the mark). It will sharpen OK, but may have a bit of a gummy feel on the stones and not be as easy as carbon/low alloy steels.
Again, it’s not that it’s bad per-se, it’s that it is easily outclassed by numerous other more modern steels. It’s cheap compared to more exotic stuff, and feels almost insulting at the price you’re paying for the knife.
If the knife we’re discussing was sub $100 I’d have no issue with AUS-10/440C, but we’re talking about a $400 knife.
Presumably if you want something that resists chipping due to the high forces of the ultrasonic, so you'd pick something with quite high toughness and moderate edge retention. Maybe something like CPM-CruWear? If you prefer something with higher corrosion-resistant properties, MagnaCut?
Those are just two examples of premium steels that would be superior to AUS-10 in every way. Additionally, as I already mentioned, you'd expect a knife that is $400 to be beautiful too. It really feels like the design element was left out of this knife. I'm sure the handle has many practical elements, but there has to be something that could be done to make it look more visually appealing.
