This is still the only cup my breastfed 12 month old with drink from, so glad we found it. The valves at the tops of all other cups completly throw him off, we've tried others and this remains the only one he will use.
a few drawbacks; yes it leaks, but if you make sure the lid is within the line on the cup, it really isn't that bad. We mostly give him water anyway, and we have a dog that acts as clean-up crew, so it really doesn't bother me that much.
However, once the cup starts to get old, old in this case is a few weeks since the quality is so poor, the lid becomes difficult to screw on, more leaks occur, and liqued will randomly just start coming out of the top for no reason.
We started using this cup when my son was 9 months, he is now 12 months and we have gone through 3, I think for the price they should last a little longer. My son isn't even very hard on things.
In spite of the flaws, I am so glad we found this cup, its as close to drinking out of a real straw that you can get.