I have an OP/Tech strap (not the sling) that I bought before the blackrapid and do like the construction and the release buckles but in looking at the sling my very first thought was that having the connector on one side of the camera would leave it bouncing and wanting to twist in a way that would be more uncomfortable than having the attachment to the bottom like the BR. I also know I've frayed connectors like that - which maybe is more what is crossing my mind as a concern./QUOTE]
My experience is that the camera tends to stay in one place because it rests against your leg - usually the "v" between the camera body and the lens rests against me (not uncomfortably so); no bouncing and twisting. It occasionally rotates 90' or so but twisting has never been an issue.
My biggest problem with the Op/Tech strap is it attaches via 1 strap mount, and hangs with a horizontal load.
The strap mounts are engineered to hold half the camera's weight, and the load to be vertical, not the entire system's weight, horizontally. Also, the use of a plastic buckle gives me pause as well.
Also, if I attach my 70-200mm lens, I have to have the strap hang unbalanced from the camera, with the lens drooping down and hitting low obstacles, instead of the nice balanced set up I get when I use my BR, attached to the tripod collar on the lens.
C'mon - the tripod mount is not designed to hold
any load, much less the entire camera's weight plus a lens. I would trust one single lug far more than I would trust the tripod mount. Plus, because you're threaded through a connector, there is zero danger of the connection point coming loose.
The angle of the strap doesn't make any difference IMHO, at least on my cameras' lugs. That would be the absolute last thing I'd be concerned about.
The plastic buckles are very, very sturdy, and are the same as they use on all their systems. Metal doesn't necessarily guarantee more strength - lots of people tried using standard QR tripod mounts with their R-Strap only to find that the metal ring spread out; the lucky ones caught it before it popped completely out of the plate.
Not using the tripod socket on a big lens is a fair concern, but certainly no worse than using a neck strap. Using the lens' socket also means fiddling with moving the connector over, or paying top dollar for an extra one, which again becomes an extra pain when using a tripod. One thing I also like about the Op/Tech is that you can use it as a safety line when your camera's on a tripod, just by hanging the strap over the tripod legs (or hanging on to it loosely in your hand), in case for some the camera takes a fall. Nothing bad's ever happened to me, but I'm always paranoid about leaving the camera attached to a tripod without any tether than I can hang on to.
Anyway - all credit to BlackRapid for popularizing this style, but even as I bought mine, I was thinking (and am pretty sure posted here at the time) that they could really learn some things from Op/Tech's design. I was very happy when Op/Tech released their version.