Hi, bought one of these a couple of weeks ago, used it for three days on the hill. Very comfortable with less weight on the shoulder than a normal sling. Bit of pressure was felt on the chest but i soon forgot About that once walking. It felt secure with both hands completely free.
i found that when you unclipped the chest strap to start crawling you must remember to hold the strap with the main sling as it was catching under my jacket etc. Thats a minor detail. Apart from that would highly recommend it. Especially when you can use it as a normal sling.