Getting tickets at the times I wanted (first thing in the morning) was challenging, so I booked a slightly more expensive guided tour which included entrance and wasn't bad at all.
The inside was beautiful and colorful in ways that the other cathedrals we've seen, were not:
We did the tower tour, which had decent views, but it was still work in progress (top is still being built):
The museum attached to the cathedral gave lots of details on the history and the build, as well as Gaudi's life:
Gaudi used nature for many of his designs
Guudi also used a gravity upside down model
Definitely one of a kind, worth the visit.