When I'm riding my road bike, I never lock it because I never leave it, which is why I still have my 1980 Peugeot PXN10LE. Around town on my single speed, I needed a painless way to be able to lock it while I dash into the library or store for a few minutes. This bottle lock is perfect for that. It's more secure than a big zip tie to prevent casual theft, and that's all I need. The bottom compartment gives me a handy place to carry odds and ends and I don't care that it only twists shut because it's held in place by the bottle cage. I don't care that I must manually rewind the cable because that means I'm not carrying around a heavy spring-loaded mechanism. I also don't care that it doesn't actually hold water because I'm not riding that far (I've read this complaint on a forum somewhere!).
The cable is long enough to reach through the rear triangle, around an immovable object AND the front wheel, all without removing the bottle from the cage. I will note that an old-school Blackburn mountain cage holds the lock quite securely, the lighter road version cage, less so (with the lighter cage I might use a velcro strap to make sure it doesn't bounce out).
This is a well-executed design that will undoubtedly spawn knock-offs; some may even offer refinements. If you need long term security, I suggest good U-locks, heavy chains and armed guards that you know personally. For me, this is the right lock for my purposes. It cost me pennies over $25 here on Amazon, which is cheaper than anywhere else I found. Good riding.