Right -- it hasn't completely replaced my Garmin 410 either. I've used the 410 to keep an eye on my cycling cadence, alert me when my HR got too high (I had a suture that I didn't want to pop open when I ran), beep at me for interval training, and draw out "MOM" in a field for a Mother's Day jog.I personally do not think that the Apple Watch will ever replace a Garmin for those seriously interesting in fitness.
But, I haven't "seriously" used the 410 for much more than that. All the data I've uploaded just sits there on Garmin Connect, and I never bother to peruse it. I appreciated that I didn't have to burn my iPhone's battery for GPS mapping, but I haven't done anything with those maps apart from uploading a couple to Facebook (and what good is showing off, anyway?).
Maybe if I competed in races -- especially if I ever had a shot at winning something -- I'd be more involved with fitness data tracking. I just don't care that much. I'm happy being faster, stronger, and lighter than I was ten years ago, and I don't need reams of data or Facebook "likes" to back myself up.