I bought this U-lock last year to upgrade from a flexible cable lock. I expected the lock would be heavier, but I didn't expect so many disadvantages.
First, the mount bracket is really poor. I mounted it on the vertical bar, and it's at least the second time I need to reinstall it, since it's hard to tighten enough. The provided hex key is crap, even though Kryptonite claims it will do fine. The short segment is so short that it won't be possible to use the long segment as handle. One needs a real 3 mm key to install this properly. I even attached a rubber band to the frame to increase friction. Even though I tightened it more than once as hard as possible, I lost hope that it will even hold for good. Vibrations will eventually require a new intervention. Kryptonite warns you shouldn't tighten too much, because some frames are too fragile! Think you're lucky enough since your frame is not carbon? Still, tightening too much will cause the bracket to become distorted and the spline to get ten times harder to insert or remove. They advise to check tightness daily or weekly! Who has the time for that? If you install this vertically, expect to waste at the very least 1 man-hour on the mount over its lifetime. Moreover, the spline provides flexibility, but it increases the space which needs to be reserved for the lock. In the end, with my bike (standard size for an adult male), I can't install this lock in the inside of the frame without losing the possibility of installing a bottle mount.
Then there's the lock's keys. The keys work fine, but they have a thick plastic "handle". This is not a problem if you have keys already, but if you have no other keys, the key means you have one more thing to carry in your pockets. It's hard to leave your house forgetting the door key, but if you just have a lock key, it's very easy to forget it, and obviously often quite a problem when it happens. It would be really simple to avoid that by keeping the key in your wallet, except since the key's maximal thickness is about 5 mm, that probably won't be an option. I believe Kryptonite should ship 1 thick key and the other key should be thin.
Finally, there's the cable. I chose this model because the cable reassured me that I wouldn't lose the flexibility of cable locks. The cable adds much flexibility, but its usability is bad. In real life, you won't use that cable often. But when you're rolling, where do you put it? Kryptonite has no answer to that. If you put it on the lock, it will slow you each time you need to lock your bike. But if you don't, good luck finding another place. What I ended up doing is tying it around the handlebar, but tying it there properly requires about 1 minute each time. It's not easy to avoid a conflict with reflectors and other stuff on the handlebar. So when you don't carry it tied to the U, most of the time you end up with an unlocked cable on a locked bike. I was lucky enough that no one stole it. Yet...
Ah, and that is probably not specific to this lock, but manipulating this is dirty. I wash the lock at least monthly, and I still check my hands after every time I lock it. Also not really specific to this lock, but you need space in your frame's triangle to fit such a U-lock. I was about to order a second bracket so I could use this lock with my Garneau Cityzen Sub-0 when I realized I would need a much smaller lock to fit such an open frame (and such a small lock would be even harder to use).
The only reason I don't recommend another lock is I've never bought any other U-lock. And unfortunately, I remember spending several hours, reading several reviews, before determining which model I should buy, so... good luck!