I just wanted to share my experience getting Boarding Groups. We went 4 times over the last week and got BG's: 2, 3, 6, 15. The days we went were: Saturday, Wednesday, Friday, Tuesday.
I restarted my phone somewhere around 9:45 because it's basically a brick that freezes all the time at this point. I had the app open a few minutes before 10 in case I needed to sign in. I went all the way to the screen that tells you the virtual que is not enrolling at this time. At 9:59 I'd start refreshing close to 10am, making sure to refresh right at 10am (I had checked my phone against a world clock and my phone matched up with it). I was hitting the area where the join button would show up repeatedly, and then clicked join on the next screen as soon as it showed up.
We got the first two groups standing outside the bathrooms in Toy Story Land. Realizing that was a poor use of time, we hopped on line for Smuggler's Run the third day at 9:55ish and got the BG while in that queue which meant we waited 15 minutes for the ride. After 10am everyone hops on line for something and the wait times shoot up. The third time we were outside the line for Toy Story Mania - the cast member was actually telling everyone to stay outside the line if trying for a BG because you lose reception in the building. That was the day we got group 15 and we knew immediately we weren't getting a BG below 10 because we both swiped down on our phones but our phones didn't register it to refresh the page so we had to try again (if that makes sense...).
I don't know if there's any useful nuggets of info in there, but I wanted to share my experience. The first day we walked right on. The second day the ride broke down and we waited in the line for an hour and twenty minutes. The third and fourth time we waited 20-30 minutes on the line. People cluster around the entrance to the ride waiting for their group to be called, so once yours is called sometimes you gotta awkwardly shuffle around there asking people if they're entering the ride or waiting.