The type of riding I do covers audax rides, training after dark, day rides for sightseeing, picnic rides, group rides, and long rides to visit friends and family.
I like to have tools to fix anything that has ever gone wrong on my ancient 1970's road bike. This fits everything you could want for winter/dark riding peace of mind and audax events if you are cautious/fully self-supported like me (lezyne micro floor drive, spare inner tubes, spare light, tools for chains and Allen keys etc, extra layers, waterproofs, hi-viz race vest, many snacks/a lunch box, lock (if needed), and a small flask (300ml). The feeling of space in my back pockets is delightful and beaten only by filling that spare space with snacks.
In warmer weather, you can even carry a change of light clothing for your destination when fewer/thinner layers are needed.
I was worried about it impacting the ride feel, particularly out of the saddle, but there was no noticeable impact for me. Furthermore, it carries very well and I personally haven't noticed sway - though I do keep a Lezyne micro floor drive at the bottom of it, which acts a bit like a structural support.
If you are considering this bag, I recommend it without reservations. It looks very smart, fits what you need (without being so big you overpack), and in my opinion, is far more enjoyable than a tiny saddle bag and overstuffed pockets, or worse not having something you need because you didn't have the space. Furthermore, having one bag to remove that is easy to carry around when I reach my destination for sightseeing rides is bliss.
Adding this bag to your bike is like getting trousers with functional pockets after never having them, the quality of life improvement this brings to many types of riding is hard to understate.
Carradice is a fantastic company. I spoke to Monika at Carradice customer care to get an animal friendly/vegan version of this bag, and I must say Carradice's customer service is beyond excellent. It is by far the best experience of customer service I have ever had.
I would give the Super C Audax Saddlebag more than 5 stars if I could, it is one of the best biking purchases I have made, excellent value for money, and I suspect I will be getting the larger version eventually for different riding purposes!