The RS-4 Strap from blackrapid is touted as offering "unparalleled peace of mind and ease of access to your camera." The RS-4 is a cross-body shoulder strap that connects to the tripod thread on the bottom of a camera. With some major caveats it does the job.
With my Olympus 14-54MarkII lens mounted on my E-520 the strap is comfortable, and the camera hangs nicely at the hip. It's a very ergonomic design. Kudos.
But! There are a number of buts.
1. No instructions - if you haven't seen the video on the site on how to adjust the strap, you might have a problem.
2. The throat on the Connector clip is just barely big enough to accept what they call the FastenR. Blackrapid rightly recommends that the plastic "gatekeeper" (a piece of clear hose!) be used for safety. The problem is, this makes connecting and unconnecting the clip a royal PITA. In fact, in the promotional clip on their website - Intro to the R-Strap Video - Ron Henry is shown using the clip WITHOUT THE GATEKEEPER. I'm sure they realize that a video of them fumbling with the catch/hose combination would not make a great impression.
3. The above might not be a problem for those who keep the strap on permanently, but I use a quick release plate - the Manfrotto 200PL-14 - on my camera to fit my existing 2 tripods and monopod. And let me tell you, trying to connect/unconnect the strap from the release plates D-ring, as recommended by blackrapid, makes the phrase "quick release" an oxymoron.
4. The strap is very bulky, and makes on-camera storage in my Lowpro 200 bag a problem.
5. The bolt on the FastenR - their spelling - is too long. The longer the bolt, the greater the danger of damage if you do happen to whack it.
6. Larger lenses - the more the weight, the less my "unparalleled peace of mind". I don't know if I'd trust the camera + 50-200mm hanging off the thread of my E-520.
7. Price. At $48 plus shipping, this is, in my opinion, over-priced. For us Canucks, this turned into Can$78, plus the border taxes. Ouch!
And last but not least - service. Apparently once blackrapid has your money they don't want to talk to you! I ordered the unit, they informed me it was shipped and provided a USPS tracking #. Unfortunately 4 days later the USPS said my item was not yet shipped. I asked blackrapid for clarification, but they ignored both my e-mails. In my book, a cardinal sin. Makes you wonder what they'd do if you had a real problem. Now obviously I did get the strap, but IMO they should have addressed my concern.
General impression - I'll be keeping this pricey strap for the times I'm going "walkies" without a tripod/monopod. But for usage with a 200PL-14 quick release plate and a tripod/monopod I'll look for another solution.
UPDATE May 26 -09: In the last few weeks blackrapid has issued a replacement for both the FastenR and the ConnectR, both now in version 2. These upgrades deal with the main issues I had with the strap, ie: the FastenR is now a screw-in d-ring, much the same as the d-ring on the Manfrotto quick release, though larger. And the ConnectR clip now is lock-able, thus there is no reason to use the plastic hose as a keeper. The two together (pictured below) work very well. Better still, the new ConnectR-2 clips onto a Manfrotto 200PL-14 d-ring quite nicely, enabling easy, and quick, usage with a tripod/monopod and mounted quick release plate.
While I still have concerns over the amount of weight to hang from the thread of my camera, blackrapid has addressed the primary concern over how the strap attaches to the camera. With this fix the RS-4 strap will be my primary means of carrying the camera, and I highly recommend it.
Note: The pictures are from the blackrapid website.