This mug looks great and feels great, nicely balanced and it wont slip out of your hand. Unfortunately, it also leaks badly from the lid, which to me defeats the object of it being a travel mug. The slider in the top has a solid 'clunk' feel as if it is locking nice and tight, but both the drinking hole and air hole leak (a lot, not just a dribble or an ooze) so this has to be kept carefully upright at all times, it certainly cant go into a kids sports bag which might be thrown around or stuffed in a locker - thats what I had planned for it. It would be fine in a car cup holder though.
The other thing is that the lid is a push-on one, and on my cup it is quite loose. I wouldn't be surprised if it fell off in use.
I might still use this - carefully, not whilst driving - now that I have it, but I can't recommend it and if it had seen it in a shop where I could have inspected it first, I would not have bought it. I am already shopping for a replacement.