I like my Black Rapid sling. I like my Manfrotto tripod. Removing the plate from the bottom of the camera to switch between the two often cause the plate to go in to hiding. Not lost, but not easily found either. This accessory solves that problem since the plate does not have to be removed to use the strap.
Unlike the original thumb screw, this D-ring is made to hold the weight of the camera.
I have the RC-2 system and the R-T1 does fit, but it doesn't fit well. Removing the original screw and installing this one is easy. Don't toss the old components just yet. Use the washer supplied in the kit and e-ring ring. If sloppy fit try adding the old washer. Once installed on camera body, it will tighten up either way.
The D-ring is loose enough that it falls over while trying to connect the strap. Or open and cause issues while trying to slide on a tripod. If the pivoting D-ring had more resistance or something that just would make it 'stay-put' while transferring between tripod-strap-tripod, it would be great.