We are trying to switch over from bottles to sippy cups, but the ones I got at my baby shower seem to leak. We were using the Nuby Click Tight or Click Locks (not sure what they were called anymore because I threw away the packaging). I really liked that they had the silicone sippy spout, so it was an easier transition from a bottle nipple. But after a few uses they leak from the click lock area where the top attaches to the bottom. What sippy cups have been working for everybody else?