I have this bag mounted on a Diverge Sport Carbon bike. The mount is secured by a plastic coated wire and routed so that it prevents the bag from sagging down at the front. The bag can be locked by key to the mount or set as just a push button release when you are always close to the bike. I choose this bag as it has a low enough profile that with the addition of a handlebar accessory bar, a headlight can be used above the bag.
I use it as a seat side bag on my tad pole trike, I like it very much as I can get into it as I ride and it locks. Granted the lock that holds the top can be cut; it is still a deterrent to someone who is looking for a quick grab and run. The bag is designed for the handle bars and not for my use but I was able to modify my side bar and it works well for me.
I wore out an earlier version of this bag - like 20+ years old and lots of international touring! One problem with that bag was the metal snaps used to secure the lid became very hard to open. The new bag uses magnets which is a big improvement. I also really like the bright yellow treatment. 'Conspicquity' is very important to me - be seen! One thing I don't like about the new design was the elimination of the front mesh pocket - handkerchief holder! But I was able to salvage my old pocket and get it to fit on the new bag with a little scissor work and prying the plastic pieces that hold the new bag together.
Arrived as planned. Paid special attention at the detailed installation instructions and everything went smooth. The mounting system is especially clever and enables to install / remove easily. It is the right size to bring a few things without having the tendency to overload it. Think of your front light ahead before ordering. I slightly moved my handlebar mounted light
I saw a review online where the dude was saying that it was hard to get the bag to close. I don't know what his problem was, but mine closes almost automatically. If I swing it anywhere close to closed, it will literally fall into place and the magnetic snaps click right in. It's great for one-handed operation while on the bike.
I bought this for a bike touring trip but sadly, it arrived the day after I left! That said, it is an attractive bag and seems well built. I like the fact that it has a solid insert to hold its shape (unlike my partner's bag) and the inner zip pocket is convenient. The lid is easily opened with one flick yet is secure when closed, so is a nice balance. It is also light, and doesn't 'dominate' your handlebars.
I have two minor critiques. First, the insert is helpful for holding shape when carrying something heftier in it: for me that is a camera, but the bag seems a bit small for carrying a modern DSLR and mid-range zoom (with a small prime lens instead, or an older film camera and mid-range zoom it is more than sufficient). It fits, but eats up most of the space: get the 7-liter if you want to carry such a set-up. Related, the insert could be a bit more robust but that would add weight. And the bag should include the clear top for inserting your printed itinerary.
Overall a very nice bag. I used Ortlieb Backroller Plus panniers on the journey and they were flawless. Like the build and design of the Ortliebs: I see why these are the most famous cycling bags. Should I size-up (I hate upgrading -- buy right the first time -- but I have several bikes so it is helpful) I will likely get the 7 liter version.