The locking mechanism is a little large for what it is but not a deal breaker. It's actually much lighter than I was expecting, which is nice. The alarm is loud enough that it would be effective against theft. There is nothing on the lock that will scratch your bike. The app does seem to be pretty responsive and quickly locks and unlocks and was very straight forward to install.
My main concern with this lock is that you can be pretty far away from the lock and the auto unlock feature activates. So for example you could lock your bike outside of your house or wherever you are and you may unintensionally unlock your bike if you get anywhere near it, even while inside. This can be remedied by disabling auto unlock or turning off your Bluetooth, but at that point, you may as well buy a conventional lock because you disable the primary feature of convenience that you purchased this lock for. If they could just dial back the range to around 5 feet, this lock would provide the security of a dependable lock, with the added convenience of the Bluetooth functionality.

I'm no expert, but I do wonder if it could be the better the Bluetooth in your phone, the worse this issue becomes. I have a Galaxy 7 edge (not that new) and I can be almost anywhere in my house and unlock my bike outside.

To start off, Nuvending gave me this product for free in exchange for an honest review. This lock arrived very quickly and the packaging was still in great condition when it arrived. The lock itself seemed to be built of good quality and had a nice weight to it. The reason why I'm giving it 2 stars, it would be 2.5 though, is because the app wasn't designed that well, and after I connected the lock, i took out the batteries to test out the alarm, and when I put it back in the alarm went off and I could not get it back into the app to fix it. This may have been the lack of instructions or the actual lock. I will update this review if Nuvending contacts me about the problems. In conclusion I would perfer just a normal cable lock.

Pros:
-Seemingly great build quality
-Great idea
-Really loud alarm

Cons:
-App not designed that well
-Confusing to get started
-Wouldn't connect after alarm

I got the Nulock Keyless bike lock in exchange for a review (firstly for my site- LearnToRV and secondly for here on Amazon). While it was provided to me, I try to be unbiased. That said, let me start with the negatives:
- as mentioned by others, 31" is deceivingly short especially if you want to lockup more than 1 bike at a time (and at the price of these, I'd really like to lock multiple things at once!)
- the chimes/chirps are annoyingly loud (the device chimes when you lock and unlock it- these could be a lot quieter)
- the notifications from the app quickly become excessive and you'll turn them off
- the fix for the security issue in another review is inelegant- they disable a master reset code entirely; if you forget your code, you now have an expensive brick; but solving a secure master security reset is tricky
- and lastly, the key feature of this lock is also an annoying negative- having been through 1 set of batteries dying, I can tell you that the answer of replace batteries is a hassle when you just want your bikes for a bike ride.

The pros are there, too:
- the biggest and most obvious one, it's keyless. Between my wife, daughter, and I- one of us always has a phone on us and thusly, always have a key for it.
- the app is fast to load and connect up with the lock - I'd be willing to say, it's just as fast as a "dumb" keyed lock
- the jostle/cut feature seem like a great idea, though I'm concerned I'll be that idiot with the lock blaring in the middle of the night; I really need to test this feature during the day sometime to see how sensitive it is
- the steel cable is high quality and seems durable
- overall, this lock has spent a fair amount of time outside for me and I've been happy thus far

It annoys everyone around until your bike is stolen and then it's a minor annoyance. Now I'm out a $200 bike, and a $40 lock.

I've only used this a few times but so far its working as described. Be careful with moving it without disarming, the alarm will bend your ears! The cord is kind of short but suffices to get it through your rear wheel, around the frame, and around any standard bike rack. If you're looking to secure a lot more you'd probably buy a second to secure the front wheel anyway. App is easy to setup and you can set it to automatically unlock when you are in bluetooth range so you don't forget and scald your ears.