Same experience here. When I heard about the Apple Watch, especially the price, I thought "who would pay so much for it?! Maybe I'll consider when it is half the price." And I thought I would never want one... right until I played with one in an Apple Store, then I bought one immediately.
Exactly the same general points as yours -
1. Haptic feedback. You never needed it, until you used it, then you don't ever want to go without it. I have my phone on vibrate most of the time, so I most easily miss calls or text is at home when I leave my phone on my desk, so unexpectedly the Apple Watch is most useful at home!
2 & 3. Same, seeing the weather on the watch is so useful that, again, one wouldn't thought it would be that useful until one had it. And able to see text messages by just lifting my wrist, same with reminders and alerts, is very convenient. I never thought that would be a big deal until I got used to it.
4. Health - it might be just a fad, and sure, fitbit might work better. But I would never have bought a wearable device just to track my exercise (which happens too infrequently to worth a dedicated device), but as an added bonus on top of the above, it does add value.