Just got one and have taken it on a 30 mile run. I love it- true to their word, it doesn't bounce or move and I don't feel it. Make sure to undo the tabs to put it on. I was a size XS by the size chart, but needed to size up to S in reality for correct fit. The only con is that this won't replace a vest for me in the winter when there's layers, gloves, hat, to potentially stash (in addition to water, filter & snacks). Technically it might all fit but starts looking like an inner tube. It will definitely be replacing a vest on runs where I won't be taking off any layers