I've found companion planting beneficial, but have had terrible luck with the corn aspect of 3-sisters. It seems best suited for warmer US zones (6+), where corn can go in the ground well before beans. Otherwise, the beans will quickly overtake the corn.

I always have some tomato cages ready as backup, because even if the corn is big enough to support the beans, a gust of wind can blow it all over.

Also, deer eat corn shoots. Damn you, deer. Damn you.