A few years back, I was Unfortunate enough to be in the same 10'x15' room with a few friends when one of them was stupid enough to ND an AR pistol (5.56 NATO). Luckily he was just smart enough to obey rule #2.
My ears rang for about 15 minutes, and I had a slight headache for about a half an hour. I didn't suffer any noticable hearing loss, but I wouldn't be surprised if there was some.
It was definately loud.
I can't inagine it was less loud than a 357mag would be.
That was it. Nothing else happened. The roof didn't fall in from the concussion, and no furniture got violently repositioned.
About the only thing I thought about for the first few minutes following the ND was, "Did that actually just happen?"