What Maraad said! It was a full 15 minutes before I was able to select tickets that went to the payment screen. Here's how it went (pay attention if you're trying on Saturday!):
1. Started refreshing a few minutes beforehand.
2. Saw tickets available on the dot, & selected my # of tickets & was placed in waiting room (DO NOT REFRESH while in the waiting room).
3. Eventually, got kicked from waiting room & saw that tickets were unavailable. Was reminded by some tweeters not to give up.
4. Kept refreshing. Many many times the ticket amount would be "unavailable" but every so often there would be a drop-down with varying numbers of tickets available up to the max of 4. Selected my number and hit "order now." Got returned to the ticket page where it said "unavailable" again, or occasionally another drop-down box. I was never returned to the waiting room.
5. Eventually, at 15 minutes, saw the pay now button, dropped my jaw and went into hyper-focus mode to get all my correct info entered while the prominent timer counted down from 8 minutes.
6. Got the "You're going to Blizzcon!" confirmation screen.
Right now I see tickets are listed as Sold Out.
The feedback screen took a long time to load each time I selected ticket quantities, but never failed.
DO NOT give up too soon!
--Create a user account at Eventbrite? All I was able to do ahead of time was register email & password, but that was enough to save some time, as it was remembered when I made my purchase.
--Have your credit card number in a text file ready to copy/paste. (Note they will want the security code too.)