I have the original version of this as well. I specifically bought it for all my backpacks while out hiking or backpacking, as carrying a camera in hand for 9 hours of hiking or so each day is a bit of a bummer. Fantastic little device, however there are some caveats:
1. The rear plate that will be pushing against a t-shirt/pants/skin can become somewhat uncomfortable after a few hours. For long hauls, I've resorted to stuffing a sock under the backplate.
2. Lenses that don't lock will extend to full length, no matter how tight the zoom ring. This isn't really a design fault, but it does give me a few ideas on how to create a much better product of my own design.
3. Their claim about its ability to "fit on any backpack strap" is misleading and absolutely false. I have about 6 different packs I use often, ranging from small (~30 liters) to large (~80+ liters). Some of the shoulder straps are way too fat for the clip. When the product was first released, the company had longer bolts on order to accomodate thicker straps. I'm not sure if they ever even had any, but the last time I contacted them, I was told they would not be carrying them. So, on one of my smaller packs with thick straps, I have to use vice grips to clamp that sucker down in order to get the bolts started. Of course, this means that the strap on that pack will have a permanently squashed portion of the strap.
Aside from the niggles above, it is far better than any other option out there. For one like myself, who does most of his hiking and backpacking in the desert, the Peak Design product is the only one that won't introduce a larger surface area. For example, there is no way in hell I would use a Cotton Carrier as it is huge & not breathable at all. I won't be buying the v2 of this product as I am still a bit miffed with them for empty promises from the first version, specifically the longer bolts. Besides, there is no difference in functionality whatsoever between v1 and v2.