I wear a Fitbit. I feel like I was incepted in to wearing a watch - I never wore one before. I thought I was buying a device that tracked my daily fitness but what I ended up with was a watch that has to be recharged weekly and tells my friends how lazy I've been.
I imagine Apple will take a similar life-data approach, especially with the rumors around Healthbook (http://9to5mac.com/2014/03/17/this-is-healthbook-apples-firs...).
My parents for example both have iPhones, but neither of them would wear a watch unless it really had some extra special usefulness. What is the killer feature? I feel like the Pebble has proven that the killer feature is not that obvious because a lot of Pebble users say they stopped wearing it.