I have used one now for several years, well make that 3 as for me they seem to wear out after a bit and fracturing at the chest hub. That being said I really love this system for carrying my gear on long hikes and long shoots it really saves wear on the neck and shoulders.
One aspect though I really want to tell you all about though is their customer service. I have rarely dealt with such a-one service. Each time my carrier has broken they have sent a new replacement. After the second they asked what gear I was using and I had to get a new angled hub designed for full frame cameras (Originally I was using a d300s).
I noticed after this weekend shoot that again the hub had fractured, but is still usable. I contacted them again and once again they are continuing to be a delight. They did not even ask for pictures of the damage and acknowledged that this was a common issue to be resolved with a new version coming out on July 1st and if I could wait until then, they would ship me a brand new carrier.
Their product is wonderful, but its their customer service that will always have me coming back to see what's new and returning as a customer.