I don't own them. I have only read about them. I have read of a few folks that have them, but they were on sites like Cloudy Nights and BirdForum or binocular/optics collector sites. Never knew of a hunter that used them. Not sure why they wouldn't, except maybe they're not as rugged or waterproof(?).
Are you considering buying some, or just curious? I missed a deal a few years back on a used pair. But, even then, they were SALTY, in my opinion.
I have used them in Europe, there are a few serious roe buck hunters that use them for big fields. They are probably more common among financially elite roe buck hunters than anyone else.
There are used ones available fairly regularly on www.egun.de