This review is about 1 year post-buy. I bought Munchkin Miracle 360 Sippy Cup for my son when he was about a year and a half. He stopped taking the bottle pretty early and skipped using a cup/straw. Before this, I've tried handful of other sippy cup. The Miracle cup is amazing and a must buy for any parents. It is 95% spill proof as some liquid does get out from the pressure after sealing the top on. If this is dropped on a hard surface, liquid will spill out. The build quality is superb. These cups have been thrown around, knocked to the ground, etc, and no physical damage whatsoever. These are great even without the lid on. We will generally leave the lid off, if we are there to supervise his drinking. This helps him get accustomed to a real cup.
My wife and I always use a new cup for each hydration session. The main liquid we use this for is whole milk. I have since bought 2 set of these to alternate use between cleaning. Any used cup gets cleaned almost daily. Cleaning is pretty basic. You must pop off the cap to get a thorough cleaning. Remove and clean the clear circular rubber stopper as well. I've never had a mold problem with these. Just be diligent and clean after every use! . For a mess-free and unattended hydration, this is the best!
7/18/19 - My toddler boy just turned 4 in May and is still using these daily. I'm seeing these cups everywhere now!