We love ours but the extra effort to get them on him and stay untangled when the toddler switches sided etc means we don't use them all that much. But I wouldn't be without them for more dangerous situations eg. walking near a busy road or feeding ducks on the river bank/canal side... anywhere I feel if he were to slip out of my hand he could be in danger right away. If it's somewhere I would have time to grab his hand again I tend not to bother as the worst that will happen in those situations is for him to fall over x
If it keeps your LO safe and gives you peace of mind, then that’s great. Pros - keeps them safe, can teach boundaries when walking outside, the backpacks are cute and fun, promotes safer exploring. Cons - have seen some children just run and fall down when they reach the length, so potential to hurt themselves, some children will just flat out refuse to walk with them on, doesn’t promote hand holding, and the biggest con tends to be other people’s negative perceptions, so for me it wasn’t a con as I don’t care what people think but I know for others that could be a big factor. We used ours sparingly for a few months on and off but we’ve now got a very switched on toddler who understands when and why she has to hold my hand and walk nicely, and the consequences for not doing so.