I went to the park today and didn't even know that Express was a thing. Nobody was using it.
Also, we totally had a blast! We only got to like 4 slides, but that's because the friend I went with has bad anxiety so we didn't really maximize our Tapu times because we had to take frequent breaks. With that being said, everybody in our group had nothing but positive things to say about the rides, ambiance, and food. We got there after it opened (around 10:15 or so) and left around 2:30 but we easily could have done more had we stayed longer or actually ridden "ride now" rides while waiting for our Tapu slides.