Not sure about the health benefits of switching to soy milk full time, but it's great for overall well-being to have a balanced diet. some soy milk at least sometimes must be good for your health!
I read somewhere that we need to eat at least 37 different types of foods everyday to get all the nutrients we need. It sounds like a lot but when you start adding them up it makes sense (eg. If you had muesli with yoghurt, banana and soy milk for brekky, that's: oats, nuts (maybe 2 types), seeds (maybe two types), dried fruit (apricots and sultanas), fresh banana, yoghurt, honey, soy milk - there you go, you've had 11 already!.