I've tried plain, vanilla, and chocolate soymilk (8th Continent and Silk brands) as well as Almond milk. Haven't tried rice milk yet and I saw Hemp milk at the store but didn't get it because it was a bit expensive. It's all very good, MUCH better than cow's milk, which I haven't had plain in a very long time. I cringe thinking back to how I used to have a cup of it with every dinner, cereal, etc. I still remember how I could barely stand the taste then. The first time I tried soy milk, I tasted the difference. But I loved it- it tasted so much better to me.
I can understand how some may not like the soymilk as the chocolate especially tastes a bit chalky (but I still like it a lot!).
I think I like Silk better than 8th Continent because the taste is better. It's sweeter and has more flavor, probably because it's organic.