I'm going to be taking my Watch back to Apple in a couple of weeks time (nearest store an hour away) after my watch literally fell off my wrist recently - aged about 5 weeks. I was unpacking a cardboard box for recycyling - and somehow the box pressed against the strap clasp (stainless steel blue, push on either side to release) and the watch fell on the floor - and smashed on the corner (crack across the whole watch face - not really useable). I spent 30 mins on phone to Apple yesterday - helpful and polite - but not helpful in the end. Was going to charge me in the region of £250 for a replacement watch (whole thing needed - can't just fix glass) - but really, knowing that this was technically a design flaw (I was not being careless or clumsy, just wearing the watch (which was properly worn) when it fell off without any warning.). I've taken it off, put it away, put the Tag Heuer (waterproof!!!) back on for now. Had worn it every day and loved it. When the blue leather strap failed, I replaced it with the sports strap - which won't fall off - but that's not the point).
I was advised to take my watch to the local Apple Store Genius bar so that they could take a look at it. The clasp was not faulty I think - but should just not have come undone so easily while in use. I would not recommend the strap at all! At least an additional safety clasp should be in place so that if the main clasp fails, the watch will not slide of the wrist completely. I can't afford to replace the watch 🙁