I've been rocking the Black Rapid RS-4 for the past couple of years; never has let me down, never created any doubts plus it was always funny to swing my 5D around (with lens) to scare everyone... Yup, that's my party trick... Lol
The practicality is amazing if you're not carrying much - A trip to Thailand for some street photography, allowed the camera to be discreetly at my side. As well on jobs, events have been a breeze and since picking up a second body, I have also purchased the RS-DS2. Feels beautiful as a harness, plenty of accessibility, not too much 'swing'. I love the additional stopping clips to create boundaries - this, I have set up so I can literally drop the camera, as well as bringing the camera to my face, it's limited and feels great!
I was tempted to opt for a cheaper dual strap (a tenth of the BR price) but with the reliability that I'm used to, plus the extended 5 year warranty, it had me sold! The RS-DS2 will be getting used a lot this year!