I just got the RS-5, BEST STRAP, EVER. God it's nice to let the camera dangle at your hip, not get in the way, having your hands free, and being able to get the rig up to your eye in no time. I'm so glad I bought it. Plus it fits my iphone in the little pocket!
I bought the double and really love it for indoor when I use two bodies/two smaller (70-200) and under size lenses. When I use just one body on it when shooting my 400 I hook the extra or open side to a belt loop to keep it balanced.
I'm kind of soured on the whole blackrapid thing after all the screwing around with the various parts that didn't work and had to be replaced. After having the camera dropped twice with the first version of the hook etc... I just gave up on them. The thing seems to have settled down, but ....
I also find I tend to whack the camera into stuff more often than if I'm using my upstraps (also longer). Finally, for serious carry and use, I now use the cotton carrier which is orders of magnitude more useful anyhow.
it is too