I use this as my work everyday. I can wear it on my shoulders for limited amounts of time. It's not a bag I would take to the mall for a day of shopping, but to walk in and out of buildings for work it's perfect.
I bought mine pre-owned and have been using steadily for a month and it the leather is very durable. It has lost it's structure, meaning it has become slightly slouchy but I love that. I also love the the side pockets b/c it's perfect for quick access to a cell phone or keys.
I like the cerf much better than the GST. It's no secret, I am not a fan of the GST b/c it's not comfortable at all on me. The outer strap always falls off my shoulder and since it's meant to be carried on the shoulder I would be so annoyed at carrying it. Also, I work in a very conservative enviroment (nursing home therapy management) and the cerf is the perfect balance of function and chic for me. Good luck with your decision.