I've no doubt now, that Apple engineered the thing to withstand more than an ipx7 rating. After all, the guys designing this thing were creating a product to replace their $20k Rolexes and surely expected a certain level of performance around water, whether any of them ever used their watches to the limits of their designs or not.
I use mine when I go surfing. So the water forces are much greater than a casual dip in the pool. And while I've seen first hand that the watch is able to withstand those forces, as others have reported, I'm not confident that it's capable of that forever. Even ipx8 rated watches have to have regular maintenece to ensure those seals are working properly. The Watch comes with a disclaimer that the watch can't be tested for water resistance following a repair, like a battery replacement. I suspect much of that warning has to do with the watch being assembled primarily with glue. Both the crystal and bottom are glued on. And some of the reports of the crown seal gaskets coming out of the pin hole, give me pause as to how well these things are constructed and the quality of some of the materials used. Ifixit reported that they thought some of the materials used in the Sport watch were of lower quality than those in the stainless models. Considering I can't really have the watch regularly checked and tested, I'd just rather put it inside a case that will ensure it will last as long as I want to use it.
They may very well come out with a 300m rated water resistant watch next year, in which case I might buy it. But considering I mainly wear the watch when I go surfing, I have no problem keeping it in a case full time, as it sits on the charger ready to go most of the time, and never has to look nicer than that (I.e. The office or dress events).