I only have 1 remaining 3-screw Blackhawk. It's from the early 70's and is a 4 5/8" .357/9 Convertible. When I used to carry it while traipsing around the backwoods, I carried it with an empty charge hole under the hammer. For target shooting & plinking (which didn't involve carry) I fully loaded it. I decided not to have Ruger modify it to add the transfer bar. I rather like the old sound of thumb-cocking it and the nice trigger. I have a SBH from the first year of the transfer bar safety, and while the bluing is surprisingly beautiful, the trigger is typical Ruger New Model lackluster.
I wish I had inherited the other 3-screw Blackhawks my dad owned when I was young, .41MAG, .30Carbine & .45Colt. Sigh. I inherited a New Model 4 5/8" .45Colt/ACP Convertible from him, but the older 3-screw version was really nice.