Well it started out ok, but...

..then it didn't.
My new WMP ran good out of the box. I did notice the barrel and slide were misaligned, but I ran it anyway to see what would become of it, if anything.
Well yeah sure enough, the barrel and slide rubbed each other causing the finish on both to wear off. I was afraid of this, but fingers-crossed hoped it wouldn't.
It didn't take long. This was maybe with 150 rounds through the gun. I only ran their most recommended ammo CCI.
The gun also consistently failed to feed the second round from 4 separate magazines. But only the second round, all other rounds fed well. (?) I thought perhaps this is because of the RDS I put on it right away, lugging the slide down. The RDS is the 3moa Vortex Venom, the very same one Walther uses in their advertising.

So I wrote Walther and included a brief yet concise explanation with 2 pictures, only to have them snarkily reply "Your complaint has to be in this format!" which was like a junior high spreadsheet. Even though they obviously read my email and knew the issues, they wouldn't even consider anything until I did that. Their 'format' is woefully inadequate, takes longer for them to decipher than my original brief email, and allows limited ability to communicate effectively, but I did it anyway.

They send me a rma and a label to print and send out via FedEx. I do it. I get the WMP back about 2 weeks later.
They did nothing with the slide, and just threw a used barrel in it. The barrel was filthy dirty. It took the brass brush and about 7 patches before it started to get shiny again. It was also scratched up. The barrel is still misaligned just as it was brand new. Of course, the serial # on the barrel is now different than the rest of the gun.

I have yet to shoot it, I'm so discouraged. Inevitably and obviously it can only get worse as the barrel and slide will continue to wear on each other. I will try it without the Vortex and see if it feeds better, but I'm really not expecting it to. The Vortex is a tiny RDS and weighs a whopping 1.05oz.

I'll tell ya kids this has me re-evaluating my status as a Walther customer. The WMP was not cheap. I paid $475 for it. $475 will buy you many other fine firearms that aren't problematic.
It's the same reason I don't buy German cars or Harley Davidson motorcycles. It's not so much the product that's the issue, it's the legendary and well-documented terrible customer service that keeps me away.

I know what you're thinking. This is an Umarex product and blame should be directed there.
But I didn't buy it from Umarex, and I didn't send it to Umarex for repair of what is obviously a legitimate complaint. No, Walther owns both of those.
This was my 4th Walther purchase. Probably be the last one. Most definitely the last Umarex. But I tell ya this; When this new barrel quickly becomes finish-worn like the original one, it will again go back to Walther for repair, but now I'm calling and talking with a supervisor. Will it do any good? Probably not.

You'll notice in the nose pic of the barrel and slide, the lousy fit of the entire thing. Barrel to slide, slide to frame, guide rod.

@balance is right about these things. They're a real crap shoot, and like Vegas, the odds are not in your favor.