Positive thing about soybeans: all eight essential amino acids.
The thing that I'm not liking about soy beans at the moment is the relatively large amount of phyto-estrogens. Basically, there has been some research to suggest that soy formula as a baby causes precocious puberty. My daughter began precocious puberty before she turned 7 (and she was a soy formula baby). She's now 9, and it hasn't progressed into puberty yet, but we didn't discover this link until recently. She's now completely off soy just so as not to upset things further.
Of course, animal products contain hormones, too. Since she's not willing to go vegetarian yet, but she is willing to give up soy, we're avoiding soy with her for now. I'd rather her have the soy and not the animal products, but I'm not going to fight her on it. I can only set the example, now...
Personally, I prefer a beans + rice combo instead of soy.