Double camera straps are definitely my choice. Having two cameras is faster than swapping lenses. Normally I have a 24-70mm on one side, and a 70-200mm on the other. I've had the Black Rapid double straps for quite some time now. At the time, it was the best thing I could find on the market, but I guess it's just a matter of time before someone else 'builds a better mousetrap'.
Rod sends in his review of the new CarrySpeed CS-Double straps, and there's no doubt it's definitely beefier than the BR's. The new CarrySpeed CS-Double padding looks pretty sweet too. Not very much padding over on the BR side. It's some rubber bubble type padding called Octopads to aid in grip and said to deter sweat by allowing air to vent. (I don't sweat much, not a problem for me).
Of course the real deal maker is a quick release adapter that still allows access to the tripod mounting hole - something my BR double strap totally lacks.
A tripod mount on a quick release adapter? Yeah this makes total sense. Even though these straps are convenient to carry two cameras, most pros still need quick access to a tripod or monopod. While the BR straps will run you around $130, the CarrySpeed CS-Double will only run you a nice
$70 US. Actually just checked and the CS-Double is on sale right now for $54. [Thanks Rod]