We got to the Skyliner both days around 8:10am and there were maybe 30-40 parties in front of us both times. They brought us up to the loading platform around 8:30. On one day, the Skyliner started running around 8:45-8:50 and we were in the park by 9:20. The second day, the Skyliner started running at 9am and we were in the park by 9:30ish. Both days worked out fine. The first day we did Slinky Dog with a 10 minute wait, Aliens, and Smuggler's Run all before 10am. The second day we did MMRR with a 30 minute wait, posted was 45 minutes.
Our experience was before the ROTR boarding group changes,. With the boarding groups now going live from anywhere at 7am, the urgency to be inside the park prior to 10am is much less. IMO, there's no longer a reason for people to line up at the Skyliner that early anymore. There's still a benefit of being there when the park opens around 9:15ish because the lines are lowest then, but I would not break my back to get to the Skyliner by a set time. If we were going in the near future, we'd probably shoot for 8:30ish. I would say its totally doable to get on Slinky Dog with a less than 30 minute wait, especially if its a weekday.