I think the verdict was correct. Under Florida law (as would be the case in most states) the state had to prove beyond a reasonable doubt that Zimmerman didn't have a reasonable belief he was acting in self-defense when he shot Martin. In my view the state didn't come close to meeting its burden. The prosecution attempted to pick away at Zimmerman's version of events but never offered a compelling alternative. This simply isn't enough to meet the proof beyond a reasonable doubt standard. This was a very weak case. Cases this weak are not normally prosecuted which naturally leads to suspicions of improper motives on the part of the prosecutors in this case.
On the other hand I don't agree that this case had nothing to do with Florida's "Stand Your Ground" (SYG) law. SYG laws in general encourage (by not discouraging as in "duty to retreat" jurisdictions) people to get into violent confrontations while armed. This will inevitably produce more shootings like this one (even if the defense didn't need to rely on the SYG law in this case). It should be noted that in a "duty to retreat" jurisdiction Martin too would have had a duty to avoid a violent confrontation (as it appears he could have done by going inside when he got home instead of reversing his path and confronting Zimmerman). Encouraging people to stand their ground can get them killed. You can argue that the negative effects of SYG laws are outweighed by positive effects but I think it is disingenuous to argue that there are no negative effects. For my part I think the law should encourage (within reason) law abiding citizens to avoid trouble. So I generally favor a "duty to retreat".