Before I discuss how well it performed, it's worth pointing out that I was using it to haul a monster lens — the Canon 70-200mm f/2.8L IS USM — which weighs in at ~3.5 pounds (with the tripod mount). I should also note that I was shooting in Santa Cruz, where it was 82° in the middle of November!
I know what you're thinking, you already have a strap and are reluctant to drop $50 on what looks to be just another strap. Understood. But, you have to realize that the obvious simplicity of this strap belies its practical genius. I won't bore you with a multi-paragraph discussion of how it works (you can see for yourself in the videos; briefly, the strap is worn over your shoulder, and the camera hangs upside-down near your hip and the small of your back), but instead will focus on why it works well.
I appreciate that a strap like this appeals strongly to those who carry two cameras at a time (i.e., you hold the presumably lighter setup in your hand, and then keep the heavier kit cocked and loaded on the R-Strap), but it also is great for people like me who rely on just a single camera.
The first thing I noticed was just how natural it felt to have the camera hanging at my hip and upside down. As previously mentioned, on this particular day I was shooting with the hefty 70-200mm lens; given its size, I attached the R-Strap to the lens' tripod mount, which allowed it to rest almost parallel to the ground. Very nice.
Despite the great weight of the lens, I quickly became comfortable — both physically and mentally — with the setup. Don't get me wrong, in the very beginning it took no small amount of courage to put a large amount of faith in the R-Strap's ability to hold the lens. That's not to say that I was worried about the build quality of the strap, but rather that I'm anal about my toys and all too aware of their cost. To that end, throughout the day I constantly checked the "Fasten R" mechanism to make sure it was tethered securely to the camera (it always was, but I'm sure, as with any screw-based system, enough movement could persuade the screw to start rotating counter-clockwise).
As the day wore on, I became increasingly comfortable with raising the camera to shoot, and then, when finished, just kind of "dropping" it against the bumper (causing it to rest exactly where it was before the shot). These motions actually are at the heart of why the strap is such a joy to use. Because of the way the connector glides along the strap (and because the camera hangs upside-down), going from not touching the camera to shooting is a quick, easy, and dare I say fun motion.
It was hard to over-appreciate that I was walking along the beach and not thinking about holding the camera or feeling it bounce against me, and all the while knowing that it was there and that I could call on it at a moment's notice.
The ability to put the camera "behind" you and just kind of forget about it is very liberating. For example, as I was walking along the main pier in Santa Cruz, I decided I wanted some fried calamari and a beer (truth be told, that decision was made long before I got in the car to drive to Santa Cruz). I was able to buy the food, eat it while walking around, and lean forward against the railing of the pier — all without ever having to think about whether the camera was going to hit something. OK, so that example may not blow your mind, but extrapolate the general idea to cover your use-case, and I think you'll start to understand the strap's convenience.
As useful as the strap is, there are a few trade-offs. The first is that the camera can no longer sit normally on a surface, because the "Fasten R" mechanism that links the strap to your camera simply won't allow for it. Given the velvet-glove treatment I afford all my gadgets, I don't feel too comfortable placing my equipment on surfaces at odd angles (did I really just string those words together?), and so I find this issue a bit annoying.
Another compromise you'll likely have to make is to keep your backpack-style camera bag at home. I realize that for some this is a deal breaker; indeed, when I first recognized the issue I questioned whether the strap was for me. When I really thought it about though, I was able to convince myself that I usually only use my camera bag when transporting gear between locations; it actually is rare for me to switch lenses when I'm out and about (usually because I just can't be bothered to do it), and so this is a concession I'm willing (and able) to make. Your mileage obviously may vary.
Finally, the R-Strap may prove to be incompatible with your tripod plate, and so you may have to remove it in order to use the strap. If your plate has a tripod mount, then you likely can use it without issue, but I probably would be weary of anything less secure (e.g., connecting the strap to a plate's D-ring, etc.).
In my case the good far outweighs the bad. I'm quite pleased with the strap and am very much looking forward to future improvements and modifications — I just can't see myself using anything else.