It's family style and everything on the menu comes to your table in portions suitable for sharing. You get a loaf of bread, a huge bowl of salad, huge bowl of veggies, huge dessert, etc. The server then comes to your table with skewers of meat and gives each person what they want and as much of it as they want.
The only exception to ordering your own food is if you are a vegetarian (like me) you can order noodles with tofu, but even that is a big portion. But this doesn't cost extra and you can still enjoy everything else brought to your table.
Ohana got bad reviews before I went in spring of 07 but we booked it anyways so we could see the Poly. I absolutely love it and have gone for my first night on my past two trips. Once I went with my sorority sisters and another time with my family and everyone loves it!