After reading reviews on this cap, I had expected a noisy drinking bottle! The flow is GREAT and I don't have any noise issues at all. I did drip water though the air valve first drink, but after a little adjusting it was good to go. Just try and keep the air valve above the water level and facing up (suck tipped horizontal, don't pour into your mouth) , and don't over-tighten the lid and it will work amazingly! Oh, and it is a perfect fit for my 750ml stainless steel Otterbottle brand water bottle!
The reason I bought it is that I have a loop cap and I manage to dump the water all over myself almost daily! Even when standing still! I didn't buy this thinking it was leakproof, and it is not. But it is DRINKABLE!!