My pre-order wasn't the smoothest experience either. I was shift+F5'ing the page but it wasn't coming even after 1pm, opened it in a new tab and it worked lol. I'd saved the pre-order the day before, but decided I wanted to change from a silicone to a leather case, managed to delete the case but couldn't see how to add a new case, so in the end started with a fresh order, which then took a dozen attempts of getting payment to go through, took me half an hour in total but managed to keep the 14th for delivery. Then later in the day, I got an email saying my order is on hold as payment needs to be re-authorised, which I must have tried 30 times over a period of time, in fear of losing my delivery slot, but the site just kept giving me a spinning circle and not giving any chance of hope on any device or browser with WiFi or 5G. In the end I rang Apple and after 41 minutes on the phone, it's finally sorted and my order is back in progress, and I still have my Friday delivery date, phew!
Watching my order status like a hawk now though! Making sure it doesn't go back on hold, but I think it's all good now.