I love that the lids are interchangeable, it limits the number of cups that I have for hot/cold drinks. The lid secures nicely so there is not leakage at the rim of the cup when tilting back. Also the flip opening is easy to open without any sticking issues. The straws that come with the cup can fit with either the flip lid or the straw hole lid, which is a nice feature to have.  
It is also super easy to clean all of the parts of the cup without worrying about missed grime. 

The only downfall is that I noticed it only keeps things hot/warm for about an hour. So when I use it I know to put my coffee in as super hot if I want it to stay at a good temperature for about an hour or so.