My personal opinion is that soy milk tastes like grass... I've tried it in coffee, alone, on cereal, but I just can't avoid feeling like someone dumped a handful of freshly cut grass in...

Almond is pretty good on it's own, but in coffee it tastes like marzipan... It's not bad, but not the taste I want in my coffee.

Oat is what tastes most like cow's milk to me.