18000 hours is basically 100 testers saving data non stop for one week. Frankly, this seems like a tiny, nay, scant amount of data.
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The lack of GPS is precisely why my wife, I, and a number of other people I know have no interest in this device. My wife bought a Garmin watch instead - the goal was to be able to leave the phone at home while jogging. The Apple Watch won't allow for that, which makes it useless as an exercise tracker, as far as I am concerned. As a status symbol and fashion statement, however, it's an outstanding device. Best thing out there, really.
It's not exactly going to be useless as an exercise tracker because it doesn't have GPS while jogging without a phone. You're still going to get heart rate monitoring, time, calories (I think). Some amount of pace is also possible by mapping out waypoints on your standard routes. Obviously there are some nice plusses to GPS for this, but it's hardly just a fashion statement.
Edit: also, 18000 hours is a little or a lot, depending on what they were doing for those hours. You should check out the video and get an idea (it wasn't 100 people wearing the watch for a week each).