we aren't to sippy stage yet, but when we do we will be using playtex. i worked in a daycare and almost every child eventually brought these in after their parents went through trial and error. they are the only ones i have experienced that are truly spill proof, they have the different stages that help them learn to use them, have straw and sippy options, and don't have too many parts or elaborate pieces.
We used the Tilty cups or the Take and Toss straw cups. DD refused to use a cup with a valve, and quite honestly the idea of turning a cup upside down or way back to get the liquid out seems like it would make the transition to a regular cup harder.
Re: Rec your Sippy Cup