You know, the girls who always abuse the guy they like? Some examples are Sakura [Naruto], Kyou [Clannad], and Kaname [Full Metal Panic]. I like some of them, but others are just too mean.
Wasn't a tsundere someone who acts cold, but has a soft side deep down? Like Uryu from Bleach? I don't think Sakura really fits the description. SHe's never been cold, just violent. And her 'soft spot' has always been plain as day.
I don't really have much of an opinion on tsunderes. It really just depends on the character themselves.