It seemed to work well enough for the Disneyland half. I was ready to go right when the second hand hit 12, but the site went down anyway. When I finally got it to load, it transferred me to active and there was a message along the lines of, "Wait time: 7 minutes. There are over 100 people ahead of you." Once it was my turn, I had 20 minutes to complete registration, which was quite generous, and that was pretty much it. In past years, I've read about people getting to the registration page but then finding out the race sold out before they finished registering, which was something I get worried about. But the fact that I had 20 minutes to complete my registration once I started assuaged that concern a little bit.
I'm not sure what happens if it sells out while you're in the queue, or if the system even lets you go to the registration page if it sells out while you're waiting.
Hopefully this helps someone who's registering for Wine & Dine who hasn't experienced this registration system yet.