I bought three of these for the family.  Occasionally it gets really hard to suck the water out.  If you crack the top, it will work for a very short while but the problem returns.  I have fiddled with the small valve on the inside of the lid - and then that fixes it, but am unsure what I did to get it to work.  This is a huge pain, especially on a trip when I am trying to hydrate in the car whilst driving.  Also, after only a few weeks with the bottles, the paint is starting to wear/scratch... not very durable.