I've had my 42mm SS with white sports strap for 29 hours.
1. If Apple had said the delivery date would be 24/4 in my confirmation and if I hadn't spent 24 hours a day on these forums, I would have been saying that Apple is the greatest company in the world. I pre-ordered at 8:01 and it was incredibly quick and easy. No problems at all. The watch was delivered on 24/4 at 10:54, which was in the one-hour delivery slot I was notified about at 7:00 by the carrier. Flawless. Except I was given a ridiculous two week delivery window and spent two weeks stressing about it.
2. The packaging and box are beautiful. I'm not sure what I'm going to do with them, but again flawless. Except they really should have made the box a charging stand like they did with the Edition box. Otherwise it's just a very pretty waste of plastic with no real ongoing function.
3. Initial impressions were negative. Despite my overwhelming excitement, I was disappointed by how small the watch was. It looked so much bigger in the photographs. Indeed, I checked the side of the box, the base of the watch and I even measured it, because I was convinced I'd be sent a 38mm by mistake. Having said that, as an object it looks and feels beautiful. It oozes quality.
4. The sports strap is so much better than I was expecting flawless. Indeed, I like it so much I've cancelled my orders for a blue leather loop and a Milanese loop. They are a lot of extra money and I'm totally fine with the sports strap. The white provides a stunning contrast with the black face of the watch, which means it looks good even when the screen is blank. It's incredibly easy to swap straps: very good design.
5. The OS is surprisingly complicated. I'm pretty tech-savvy but I still push the screen expecting a force-touch is necessary. Sometimes it is. There's no way to tell. Then there are all the settings: on the watch and on your phone. It was really not obvious that to get another World Clock I had to use the Clock app on my phone *not the one on the watch, nor the one on the watch app. Adding friends one-by-one is clunky.
6. The haptic/taptic/whatever has been disappointing. People described it as some kind of amazing new technology. I can distinguish two types: a general vibrating/buzzing feeling like on any phone, and a prod.
7. The Maps app is awful. It seems to assume I'm driving and I don't know how to tell it I'm walking. It says things like "Proceed to X street" but I have no idea where that is and the map onscreen is tiny. The turn left/turn right taptic thingies are indistinguishable to me.
8. I've spent hours customising watch faces. I can't decide which to use. They're really great. As a watch, the Apple Watch rocks. I love it. Try it in a dark room: it looks amazing.
9. I've been hugely impressed by the watch's ability to know when I want to look at it and when I'm done looking at it. I've almost never had to force the screen to come on. This was a major worry for me before I got the watch. No more.
10. I need to figure out what this watch is really for. There's no point duplicating things my iPhone can do. Especially things it can do better. I have a 6+ and I don't like taking it out of my pocket when I'm outdoors walking the dog, so I like getting notifications on the watch and looking at glances for weather and for the pedometer. I'm not yet sold on other apps.
11. I used the watch a lot yesterday. It ****ed up my eyes. Seriously. The resolution started looking really bitmapped and not at all retina. I asked a friend if it really was retina. But then my iPhone and MacBook started looking like that. Basically the focus required to see the tiny watch screen clearly had made my eyes lose the ability to focus and everything was looking blurry. Clearly I need to ration how much I look at the screen. But then it's supposed to be an occasional device: after the first couple of days I didn't endlessly stare at the last watch I bought.
12. Receiving someone's heartbeat is really creepy. I tried it with a friend. I can imagine it might be intense with a lover, but it's just weird otherwise. Drawing pictures is really hard. I think that'll all get old real quick. Poking/tapping a friend is quite fun, though and could be useful.
13. Siri was a bit buggy. I tried demonstrating it to a friend using "Hey Siri" -- nothing happened. Over and over again. Of course, now that the friend's not here, it's working fine again.
14. The health/heartbeat info is interesting and motivational. Love the iPhone Activity app. Not sure I believe all the numbers, though.
15. Overall I'm feeling more settled with it and I'm happy with my purchase.