On Sunday, despite an advertised ride opening time of 10am, I didn't see a single ride operating at this time.
Certainly Valhalla and Grand National were advertised as opening at 11am, as seems to be standard, and as mentioned above. But also Icon was advertised as a 10:30 opening at the ride entrance and certainly The Big One, Infusion, Big Dipper and Avalanche were not operating until after 10:30 either (like I said previously I didn't see a single ride operating with guests before half 10 - was standing in a pre-queue for Icon).
Staggered opening was poorly communicated and it was shocking that the park was advertising a 10am opening when clearly it wasn't ready on time. They'd be better off just sticking to 11am openings and having everything ready, in my opinion. Don't know if this was standard practice but it was poor.