Bests & Worsts Reviews from Amazon

I gave it a 4 star so clearly I it. It does just about everything I expected it to. However there is a surprise factor that nobody seem to address. The mouth piece that you drink from is difficult to clean, I've only put water in this bottle (cold). Because the soft plastic that create the autoseal effect is always behind hard shell cover, if you pay close attention when you push the button to drink, you'll so discoloration, looks like mold to me. I've tried so badly to clean it. For reference, I've had it for almost 6 months. I notice this about a month ago. I've added a flipped over photo so you guys can better see what I'm talking about.