What happened? They grew up. I hope that's truly analogous for boys to men.
I loved that each toy moved accurately to how one would imagine to them to move in real life. They were each distinctive and realistic but as toys which helped add believability to the movie. It's Pixar so (of course) there was a tear-jerker moment- don't even try to not cry because you won't be able to resist.
Also: what toy smells like strawberries?! Looks can be deceiving!
8/10 points. Go see it.