I was looking for a lock for my bicycle - one which was reasonably secure but small and light enough to carry easily for use when stopping at a shop or cafe. (I have larger locks for overnight use.)
I found this lock to be the ideal solution - many cheap locks have flimsy thin cables, this is fairly thick and would need some serious cutters to break it. The cable is short, meaning it will only secure the frame and possibly one wheel provided you can find a suitable railing to lock it to. The advantage though is the lock is light and easier to carry.
If you prefer a key, then look for another version - I prefer the combination lock as it means I do not have to worry about always having / not losing the key - I only have to remember the combination!! The tumblers (4 off) are large with a definite click when rotated through each digit (10 off) so it is easy to use - useful on cold mornings!
There is nothing for mounting the lock to a bicycle, but it is small enough to fit to your pocket or a saddle bag. I often hang it round my neck - not as bling as a chain but can't have everything!
While nothing is 100% secure I have a lot of faith in this lock, and the Abus name in general. In my opinion it represents excellent value for money as well.