Egg laying machines. Often 5 or 6 large white eggs a week in their prime. There are days my 5 leghorns lay 5 eggs, while my 20 or so other adult hens only lay that many combined. So they're kind of the go-to laying breed.
Some will say they're typically healthier than popular hybrid layers, although that probably depends on specific lines/birds. Ours have been quite hardy. They do have the big single combs so super cold weather can lead to frostbite.
They have a reputation for being flighty/shy but one of ours loves attention. They tend to stay smaller and don't eat as much as larger breeds, especially nice given how they put out eggs. Ours tolerate confinement but like to range. In a mixed flock, ours tend to be towards the top of the pecking order despite their smaller size.
Overall, they're popular birds for a reason and no laying flock should be without some in my opinion. I hope you enjoy them (and are ready for a lot of eggs).