Revisiting this thread after spending some time to sharpen and hone/strop some knives, including a few that I carry often. Two are M390 and one S35VN. One of the M390 is my range and camping knife, and somewhat of a beater. I use all of my knives, mostly for opening and breaking down boxes, but all of them are used, no matter the price range.
Have discuss differences in steel before, but that's something I've definitely noticed in my recent use and sharpening. It may have to do with the exact steel or company who produced, as well as the blade profile/grind, but I'm definitely noticing that the M390 blades keep their edge a lot longer than S35VN and aren't that difficult to sharpen. At least based on common ratings compared to other supersteels.
One knife with M390 that I carry often is a ZT 0770CF. It was one of my first ZTs and bought from a 2a forum member. This is one of the M390 knives that got me really interested in this steel. It doesn't get beat up as much at my ZT 0566, but it gets a lot of use. I was thinking it needed sharpening. I had just finished sharpening my 0566, so I had the Wicked Edge out. After cleaning the blade off (mostly tape and adhesive residue), I decided to strop it first and see what that did. After some stropping, it was sharp enough to still shave hairs off of my arm. I was surprised since I had used that knife a lot in the past many months since last sharpening.
The other M390 I used often is a Kershaw Dividend. I think I got it for around $70 a while back. For that prices, it's been great. The "hardest" use it gets is at the range and camping. It definitely gets a lot of use, and more than boxes and tape. That one gets sharpened quite often. I should try stropping here and there.
The reason I busted out the Wicked Edge was the ZT 0566, which is S35VN. That knife is my carried the most and most well used. I "think" I can noticed a difference in how quickly the edge degrades through use compared to M390, but just might be due to how much I used this knife.
I have a Lion Steel M390 that I don't carry as often. I might have to try carrying that one more often and seeing how it compares to the ZT 0770.