iPhone OS 3.0 is a free software update bringing 100+ excellent new features to all iPhone models. With the announcement of iPhone 3GS, if you are confused on what features are exactly in your particular iPhone, help is here.
Apple has published a chart with a list of features and its compatibility with different iPhone models.
You can read more on iPhone OS 3.0 new features here. Also, the iPhone OS 3.0 User Guide will be your best bet to finding little buried in features.
