I've been wearing a Garmin or Polar watch for the past several years (run 30+ miles a week), and just recently got an Apple Watch.
For a serious runner, the Garmin watches are a lot better, but the truth is that I'm not really a "serious" runner, and Apple Watch is more pleasurable to use in a lot of ways.
I thought I would mind having to charge it every day coming from a device that needed to be charged about every 6 days (and that's including 24-hour HR tracking and 4-6 runs a week), but the truth is that I don't. I also thought I would mind not having all of the metrics or customizability that the Garmin offers, but the truth is that I'm not a competitive runner, and my V02Max isn't anything more than a curiosity. And, sure it's nice to be able to choose from a million different data fields to display while I'm working out, but the default ones on the Nike Running app are pretty close to what I chose in the first place.
In the end, a lot of the things I thought were non-negotiables ended up not really being a big deal. Apple has really nailed the Watch user experience in lots of little ways.
I intentionally held out when all of my friends bought the original Apple watch (and most subsequently sold it), but I'm noticing that an increasing number of people have adopted the watch a hardware revision and a few OS iterations later.