I used the Ramset trigger style to secure my soleplates to the concrete floor in my basement. It worked like a dream. On occasion I would hit a spot where the nail wouldn't get totally driven. i just put another shot in it and hit it again and it went down.
Personally, I feel like unless you do something really stupid like put it on your foot and squeeze it is a relatively safe tool. You have to apply pressure to get it to shoot. Definitely use glasses and hearing protection. Otherwise hold it straight up, apply pressure and enjoy the smell. I agree that i would not use it on block walls