Yes, I have used it. On the air. And been understood – and understood the responses. It’s been a while, so I’d need to refresh things some to do it again.
For those unfamiliar with the terminology, this is a straight key. There are other arrangements that allow varying degrees of automation. I never got used to any of them, and thus this was my key of choice. The odd bit to the side (lower in image) is a shorting bar, which when moved to the bit closer to the key’s ‘handle’ shorts thing so it’s like holding the key down. This is useful when making adjustments to the transmitter.