I'm not a knife guy.

What is considered to be high quality Damascus steel as far as edge retention and ease of sharpening ???

Is there a target Rockwell hardness target for Damascus??

Is a Damascus steel steel made up of 1095 and 15N20 considered to be top flight steel ?

It can be difficult to get an accurate hardness measure on damascus.
A popular and excellent damascus mix is 1080 or 1084 with L6.
One consideration is that the two steels have similar heat treating characteristics and the 1084/L6 does just that.
There is also a stainless "damascus" though not true damascus -Damasteel .That works well if you want a stainless version.

Respectfully........
What's the big deal with damascus steel blades? Do they sharpen easier??....hold edge better??....resist "wear" better??....maintain rigidity better??....flex better??....
Or, is it a gimmick?

At this point in time nothing is gained except that some beautiful designs can made.In the old days the process was to make the steel more homogenous. Vikings used it 1000 years ago.
Another way to get excellent blade with beautiful design is to make a laminated blade with high quality center covered on each side with damascus. The damasteel I mentioned ,[www.agrussell.com] I use as my kitchen knives and always get compliments !

Thanks!!....I appreciate the information.

Damascus knives have the same characteristics as other knives. Some perform very, very well.
Others; not so well.
Just as there as all manner of "custom" mausers out there; some may perform and look very differnt from others.
Research your knife builder every bit as carefully as the guy that is going to build your next rifle.
Attention to the details; welding, forging, and heat treat,; are everything in how a damascus blade cuts.
M