I haven't used one, but they look like they might be ok for quick hip carries with a kid who can hold themselves up, but only so long as you have a hand free to support them because that little sling is not going to provide a whole lot of support up the back.

A ring sling would be better. There are mesh ones if you're looking for something cooler or for in the water, though they're not terribly comfy to use for long periods of time.