I've owned this bag for around three years now and have used it on and off a lot in that time, mainly for city riding as the only bag. There are some great things about it, and unfortunately one massive negative which means I wouldn't recommend it to others.
The pros: The bag is well made, as you'd expect. The fixings are all of fantastic quality and the bag looks the same as when I bought it, save for a teeny bit of fading, and the leather side straps which I'll come to in a moment. The lid has become more supple in its age, which is a bonus. When I've been caught in the rain the bag's contents have remained dry.
The cons: I primarily liked the idea of this bag as I could take it on and off easily and carry it around town with my things such as phone, keys, camera. Unfortunately, the fixings for the shoulder strap attachment are not placed well for this. If you look at the pictures the rivet attaching the leather on the side of the bag is less than halfway up the bag. This isn't great when the bag is empty but it's a disaster when the bag is full. When full, the bag's centre of mass is above the pivot, and when the bag is over the shoulder, it really wants to spin around such that the lid is pointing at the floor! Even worse I've had a camera in the bag fell onto the floor because of it. It was mostly my fault as I hadn't secured the lid but even with the lid shut I don't want my bag to be a tombola! This has happened so many times that the leather side attachments are starting to appear cracked due to the stress. It's cosmetic (I think) but is quite incongruous with the otherwise pristine bag.
In conclusion, this one flaw spoils an otherwise perfect bag. If you're never going to use the shoulder strap, then yes this bag is great. If you are planning on having it over your shoulder, then I'd probably recommend another bag. It's hard to judge purely based on the photos, but I believe that the Super C handlebar bag does not suffer from this.