Echoing a lot of other reviews - it's definitely a bit overrated and the wait can be insane (even with a reservation; I can't imagine trying without one).. but it's still a fun and memorable experience with pretty good pizza and wine.
If you go, I definitely recommend going with a group of ~8-10 people and making a reservation well in advance (I've never been for lunch but I've heard that it's more feasible for that).
There's a nice beer and wine bar next door (which, I assume, strategically at least doesn't mind that people are waiting a long time to be seated).
As long as you go with a good group of people and consider the waiting to be part of the experience, I don't think you'll be disappointed.
The biggest shame for me is that they don't have patio seating (in Phoenix it's nice enough for that almost year round). That said - it's a beautiful and central location, and if you go when it's a bit chilly out (by Phoenix standards), you probably won't mind eating inside.
I can't bring myself to give it an overwhelmingly positive review (mainly because they're so overrated) but I can say that other than the waiting (which is part of the experience if you're with the right people and not in a rush), I've never been disappointed or had a bad time there. Definitely recommend trying it out at least once.