This cup has been a great transition cup for our toddler as we have been phasing out bottles. But he wouldn't really take to standard sippy cups because he got frustrated with not understanding he needed to tip them up to get milk to the spout, especially if he was holding it and feeding himself, which we are trying to encourage. This has helped with that big time. Now he just wanders around the room sipping without any real issue, aside from when the milk level gets low and the sink doesn't quite angle right to pull it in. A minor issue really. There are some quirks about this cup though and while it works great, it is a little bit more complicated than it seems. First: It's not as leak proof as they claim. At least not without doing everything exactly right. First you have to make sure the silicon spout is in the cap snugly and is aligned properly. Make absolutely sure to look underneath and make certain that the edges are all in place and flush with the edge of the cap. If not, or there is any bulging or any part of the edge is concaved, it WILL leak. Second: This is important, but do NOT overtighten the top. It may seem counter intuitive, but we found out the hard way that if you overtighten it it will be prone to leaks. And that's because the silicon seal rests firmly on the inside (or underside I suppose?) on it's own, but if you really cinch down on the cap when you screw it on, it will push the top edges of the cup inward really tight and cause the outer edges of the silicon insert to bow outward, causing space and, of course, leaks. Tighten it until it doesn't turn anymore, but don't apply hard force. If you are forcing it, you are over tightening. Trust me, it took us awhile to get what was going on here, but once we did figure it out, the problem almost completely went away. Third: If the sink insert separates and falls down into the cup, which happens sometimes especially if your baby drops it on a hard floor, then you may find that it keeps slipping out and falling back in every time you put it back. The fix for this is simple. You just need to make sure that the plastic insert on the sink and the inside of the silicon fitting for it are both good and dry. If they are wet, the sink will just slip right out again. Take either a paper tower or a microfiber cloth or towel and wipe away all the moisture from the surfaces that meet each other - that is the outside of the plastic insert and the inside of the silicon fitting. If they are both dry, when you insert the plastic, the silicon will have a lot of friction against the plastic and hold it in place with a really good grip. Remember, wetness works against you here. Fourth: If you dribble a lot of milk onto the threads of the cup, itself, then it will dribble out a bit even after its screwed on. Just wipe the threads down until its dry and you're fine. The instructions say you can't let your toddler bite or teeth on it and...we'll you try and stop a teething baby from chewing on this thing. That's not exactly something that you can always stop. Sure enough, he's chewed holes and splits into two of these things which causes a leaky spout. Like I said, exactly how do you effectively stop a teething baby from chewing on this thing? I feel like that particular instruction is kind of a frustrating one and wish that maybe they instead made the spout a little more durable instead of putting it on us to prevent something that is near impossible to prevent. Even when we do catch him doing it and pull it out, all it takes is a sharp tooth in the right spot to pierce through so by the time we stop it it may already be too late. I feel like they should have worked on this more instead of putting it on us. Again, this is a great cup and a great purchase. But I see a lot of people complaining about the little bugaboos about it and a lot of them actually have solutions. So I hope these tips helps some people out there and you can avoid the trial and error my wife and I had to do with it. I'd recommend it highly, just keep these things in mind to make your life and experience easier.