We had problems with 3 sisters when we tried it, the beans smothered the corn, reducing yield and making harvesting difficult, however, we've been using a 2 sisters method for the past 3 years of corn and pumpkins / squash, and that works brilliantly!
The corn grows nice n tall, so crops well, and the pumpkins / squash grow lower, crop well and provide a good groundcover, reducing weeds to almost nothing!
I'd definitely recommend growing corn and squashes together! We've put a few sunflowers in aswell, to keep the squirrels from attacking the corn (they go for the sunflower seeds instead)