I'm sure the jury doesn't want "OJ: The Sequel", but at the same time, they don't want to hand down a verdict that will invalidate Florida state laws that allow for lethal force to be used in a self defense scenario.
Zimmerman will probably be found guilty of a far lesser charge than 2nd degree murder because he needlessly followed an innocent pedestrian who, feeling threatened, defended himself by turning and attacking a strange man pursuing him.
Stand your ground can go both ways in this case. That doesn't negate the outcome of the confrontation. A kid died because an overzealous guy decided to play policeman without a legal mandate, in fact, against the instructions given by the law enforcement authorities.
Both parties should have been held liable for their actions, but one is too dead for that, so the remaining party has to answer for disallowing the other his day in court.
The jury has to balance justice with the political ramifications of their verdict. Lengthy deliberation is absolutely appropriate.