Hello, not this particular style but I own 3 PSTs in caviar leather which are cut the same. My personality is rather minimalist. I love the PST, such a great size as an everyday bag; really cute for flying too.
The PST holds all my essentials, which can include an LV long wallet, LV 6-key holder, iPhone 6s, tissue pack, lippy of the day, book/kindle, small bottle of water. Sometimes an additional small toy and small pack of snack for my toddler
When I need more space, I will reach for my LV Neverfull. Not a fan of the GST.
And no, the straps do not stay easily on the shoulders (I am EU 36 - 38, 170cm tall). They slip off unless you hold on to them as they sit on your shoulders - which is a rather comfortable way to carry the bag in my opinion. I love to carry them by their straps in my hands or in the crook of my arm. Easy access with the open top; a scarf over it will tame some security concerns.
Any handbag style has to work for your lifestyle and needs. Hope you enjoy the bag if you get it.