RonDeer, Glad you asked the question, and I too would like to see a few more responses from 10mm Witness owners. I have been contemplating a 10mm purchase myself.
A few of MY observations from owning all Witness calibers EXCEPT the 10mm.
Generally, the Witness series is a fantastic value across the board for all calibers. I have owned .45 auto, .38 super, .40 S&W, and 9mm. Don't think they have offered .357 Sig yet?
10mm should develop MUCH different recoil impulses than any other bullet combo. IF EAA put the proper engineering into the gun, they MAY have beefed up the slide a bit or even the lower frame in critical areas, as well as increase the recoil rate of the return spring. I do have some concern they just took their off the shelf design, in the large frame variant, cut it for 10mm and just upgraded the recoil spring. That does leave me worried about frame durability. The recoil velocity of the slide is probably much higher than any other caliber, but I am not engineer. Not really sure of that?
That being said, I may just buy one and torture test it for the sake of other readers. It will be under warranty by an existing manufacturer. Not sure what their warranty policy is, but I would push the envelope for sure. I was surprised when Colt took the 1911 and married it with the 10mm! Never thought they would hold up, but seems that they do.
I hope that a few more people that have 10mm Witness experience will chime in. I will say that I certainly don't like or trust the new round top Witness, that has less metal on it than earlier versions....so will look for the original.
Thanks!