* Prices may differ from that shown
When you buy a large DSLR type camera you can expect it to come with a neck strap in the box from which to hang your camera. This strap is often obviously branded and made of a thin nylon weave similar to straps on a holdall and the construction means it will slowly cut into your neck causing discomfort and can also mark you out as an obvious target for theft or muggings. Granted, the latter is usually less of an issue but maybe you don't like the somewhat gaudy colouring or logos.
With my camera, I found that the free strap to be uncomfortable when it was worn around the neck, as mentioned already, the thin cross section made of coarse nylon would slowly cut into the back of my neck and the thin rubberised coating would build sweat and cause further discomfort.
The Black Rapid RS-4 Classic strap has a similar nylon strap material to the free straps, but it also has a large padded shoulder strap which is fixed onto the strapping so it won't move position from the shoulder or neck. More on that later. The padded part is initially very stiff, work to make it more pliable and you notice the outer part is made of military style rip stop fabric and the bottom is a soft woven nylon mesh which is both soft and breathable preventing sweat build up when worn. The large size also helps to distribute the weight of the camera over a larger area for better comfort.
The strap connects to your camera on the tripod socket using a metal anchor which screws into the tripod mount, to this you clip in the metal locking carabiner which is attached to the strap. When worn over the head and shoulder, the camera will rest on your hip within easy reach of your hand.
The strap also has two small clips which you position around the carabiner so that when you let go of your camera, the clips pull the strap back round the body so that the shoulder pad rests back to where you originally set it. This means the strap will always be in the correct position and you will always have the soft pad against your neck.
Another small benefit is the small zippered pocket on the pad, it is small but can fit a memory card or similar sized accessory for easy access. I have in it a small microfibre cloth for cleaning duties.
Having your camera hang from just the tripod mount is initially very unsettling, you will constantly be worried that if that loosens, your (expensive) camera will meet the floor fast. You can always put some Loctite on the screw thread to secure it but that would mean you wouldn't be able to use a tripod. What I periodically do is reach down and give a tightening twist to ensure it is locked on securely. Having said that it has never been anything but screwed on tight.
If you want a comfortable strap for your DSLR which will allow easy access to your camera, I can heartily recommend the Black rapid RS-4 Classic strap. It will take a little getting used to having a camera hanging from its tripod mount but it is indeed secure and eventually you will trust the connection and love the natural ergonomics of this strap.