To my knowledge they have not made a Manfrotto compatible plate. They have made a
FastenR-T1 which is a bolt and D-ring to replace the one that goes through the Manfrotto 200PL-14 (RC2) plate. The original Manfrotto D-ring was never designed to take a significant weight tugging at the ring. It was designed simply to allow the bolt to be tightened, not to be load bearing.
There is a risk (possibly theoretical) that the Manfrotto D-ring could simply pop out of the bolt and leave your camera and lens on the floor. I have a couple of knock off Manfrotto plates and I know for a fact the D-rings on them are not well secured. I have had them pop out when simply tightening the plate firmly. They would absolutely not handle the weight of a camera and lens. Maybe the genuine Manfrotto D-rings would hold up, but that's a chance I'm not willing to take. For the sake of ~£15 per T1 I would not take a chance of smashing £1,000s of gear.
That said, I'm not entirely comfortable with the length of the T1 bolts. They are shorter than the Manfrotto bolts and penetrate into the camera less, with about 1 turn less thread to secure the camera. Those who know more about these things than me assure me that there is sufficient metal to metal contact there, but it might be worth using a little Loctite to ensure the thread does not back out unnoticed.
This afternoon I'll be experimenting with leaving the normal Manfrotto plates and bolts in place and fixing my FastenR-3 fasteners to the underside of a couple of Manfrotto MN323 QR platforms. This will allow me to maintain full tripod compatibility across three bodies and two lenses without constantly swapping plates, bolts and connectors around and will give me a quick release for the cameras/lenses from the ConnectR-2.
Apart from all that, I agree fully with the benefits listed by others. I have the DR-2 twin strap and it can be worn and used under a coat, which not only is more covert, but also protects the gear from rain.
I also have three Optech Pro straps and a Cotton Carrier System and if I had to pick one system over the others it would be the Black Rapid. The Cotton Carrier would be the better bet for traversing tricky terrain or mountain biking, skiing etc. as it prevents the gear from swinging, but it is not quite as quick and secure to use. For most types of photographic situation I think the Black Rapid solution is ideal.