The concept behind the Stamina Bar is simply enough, it goes down whenever your character runs or attacks.  It is effected by the weight of your armor and probably also by your Vitality,  Dexterity, or Force.  When the Stamina Bar depletes, one of two things either happens: your rate of attacking or running is drastically reduced or it is stopped period.  As soon as this new feature was unveiled, the howling began.

The debates travel back and forth, some people defending the Stamina Bar and some people criticizing it to no end.  It's defenders claim it adds elements to realism to the game in that you cannot make infinite attacks anymore, it all takes a toll on the character.   Its critics say that it breaks the game, sacrificing fun for realism isn't exactly their idea of a fair trade.

I both agree and disagree with both parties, seeing the Stamina Bar in a strange light.  It would add realism, but stands the chance to subtract from the actual fun of the game.  Diablo is based on the whole concept of "RPG on the go," meaning it's an RPG that can be played and understood right out of the box.  Adding too many elements that complicate the game stands to lessen its potential gaming circle, as well as its popularity.

Don't get me wrong though, I think the Stamina Bar will be a great addition to an already great game.  Not only does it add a lot to realism, its a whole new branch of combat tactics to take into account.  Diablo II may actually have the need for tactics and strategy, unlike its predecessor.