I got the contractors metal card back when they were first released. Have used it here and there (granted, all within the US), mostly at vending machines and kiosks, etc. Works great IME. Took me a few times to realize it's really just a tap that's needed, not hold it there until something happens.

I have another contactless credit card and a transit card and usually a hotel key in my wallet, so currently unable to do the swipe-the-whole-wallet trick.