I will say it depends. Are you patient and are willing to grow with the iPhone as it gets updated? Are you willing to live with the phone in it's original released configuration before Apple does it's magic and fixes those things they know need fixed? Are you willing to hang loose until Apple finally feels comfortable that they have a handle on it before they open it up to developers? Are you willing to be part of something completely new and landscape changing? If the answer to these questions is yes then by all means it is very very worth it.
If this just isn't you then hang loose and wait until the rough edges get smoothed out and the phone starts adding features and is open to developers for real. Too many people here either don't remember when Blackberries first appeared, or Treo's first appeared, or the first generations of smart phones came on the scene. They came with nada(not jack, diddly, nothing, squat, bupkis), but after a while they were opened to development, and they improved to address customers needs. Today you can(in a haphazard and frustrating way) do most anything you can think of. The iPhone brings a completely new level of integration and tools to the consumer, but it is going to take some time before it becomes mostly all things to all people.
If your not the patient type and expect that for your $500 or $600 that it is going to wash the car, dishes, mow the lawn, and compute winning lotto tickets for you then "this is not the phone your looking for". At least not today.
The beautiful part is this is literally a handheld computer, it can be upgraded, it can grow and expand capabilities. Can you sit back and enjoy the ride as we go into a new frontier? Only you can answer that question.