Just some thoughts...

I'm looking to get a strap for my Hasselblad and Leica and I like the OEM straps. I've used them both without straps, and I'm fine with that but sometimes you need two hands to do something while you're out there shooting. It's also less conspicuous to have it on the strap down along your side when you're out and about, you can be much more nonchalant while carrying the camera than if it's in your hands the whole time. I went out on a street shoot, about 4-5 hours a few weekends ago, and although it was only the Leica with one lens, it can strain your hands to hold it for that long.