As reported here on The Travel Photographer's blog, I'm a fan of the Black Rapid R-straps and have used mine for over a year on my various photo-expeditions. Many participants in my photo-expeditions like and use them as well, however they're all wary about having expensive cameras dangling from their bodies.
One of the common fears is that the Fasten R which attaches the strap to the bottom of the camera's tripod mount gets undone. If that attachment/fastener is not tightly screwed in, it could get undone because as the camera hangs from one's body, it wiggles and swivels around; such movements can loosen the attachment. Naturally, if that were to happen, the camera and lens would fall to the ground with potentially ugly consequences. I make it a habit to check the tightness of the attachment/fastener every now and then, and a couple of times found it to require a turn.
The company produces the newer FastenR-2, but as I don't have it yet, I can't speak to whether it's an improvement or not in that respect.
Since I'm about to travel in the coming few days on my Bhutan Land of the Druk Yul photo-expedition, during which we'll be frenetically photographing the various festivals and rituals, I've decided to adopt the suggestions of many photographers...and tether a length of lanyard to the Canon 1d's eyelet (originally for the optional hand strap). I also replaced the L-shaped Fasten R with a 1/4"x 2" eye bolt from a hardware store. This makes me feel much more comfortable, since should the eye bolt get loose, the lanyard will keep the camera from dropping to the ground.
Does it look classy and elegant? No, but it's good insurance....and no, it doesn't impede my photographing vertically. Well, maybe just a little bit. Another advantage is that I can easily check and tighten the eye bolt (if need be) with one hand as I walk around.
I'm carrying my other camera (5d Mark II) in a Lowepro holster-style bag, so I don't need to retro-fit another Black Rapid strap in the same way. Even if I wanted to, I couldn't use the same method as 5D Mark II doesn't have an eyelet for a handstrap....but necessity is the mother of invention, and I'm bound to come up with a solution.
Naturally, if anyone has a better idea (or simpler), do let me know!
Note: My thanks to Alex Marino who introduced me to an alternative strap called Sun Sniper. However it's similar to the R-Strap, and has the same weak spots.