I had mine on my Speedy and love how it looks. But after having been caught by the rain a couple of times the lock tarnished within a couple of weeks and it does not shine so nicely anymore. That is when I put it in its dustbag.
I have a classic speedy where the lock is on the bag where it belongs but on my speedy b I took it off cause it doesn't really have a place to go and was more often in the way. I prefer classic speedy.
I don't have a lock for my speedy (pre-loved) and I honestly don't mind. For me, I don't like the look of the lock on the side. I also don't like how it stretches the hole. Even when I do buy a new speedy, the lock will be put away.