We used these with pre-folds and covers for my son until he was about 6 months old.
I feel like they were worth the money when he was little. It held the diaper in place well and usually stayed on. Sometimes they did fall off, or one side would unhook.
Once my little one was over 5 months or so, the size 1 was too small and we didn't end up buying the next size up. At that point we just switched to newspaper fold and that's what we've used ever since.
I think if we have another baby in the future I'll use these for the little baby period, just like we did this time.
They are certainly easier than pins, that's for sure!