I was at the last show, left rear seats in the "platea alta", slightly to the centre.
Soundwise it was quite muddy as other people have mentioned, especially rhythm guitar and voice being not as clear as I would have expected, and often Rudess, Myung and the backing tracks were very difficult to hear. Drums were clear and powerful, the best sound Mangini's had in the three times I've seen DT with him, every hit on the floor toms sounded like something out of an Hans Zimmer track.
Performance wise, I think they were really on top of their game, especially Petrucci who was constantly pointing, grinning, raising his hand in the air and generally rocking out more than usual. Only exception being Labrie, which towards the end of act I suffered a couple of choked notes and bad screams that left him quite upset and forced him to keep on the low octave for Moment of Betrayal and having trouble with the fast part in The Path That Divides (though that wasn't so bad after all)... he then sort of recovered towards the end around Hymn of A Thousand Voices and I think everyone appreciated the effort he went through to make the ending as engaging and majestic as possible for the crowd, regardless of him having a bad night. He really made the most of Our New World and Astonishing.
I might say that I didn't enjoy as much being in a theatre, having to sit down for most of it felt like not being able to enjoy the gig as much and I think I managed to annoy most of the people next to me by singing along several times during the show. It was fun, but it felt a bit forced to just stay there, sit and watch, sometimes cheering, sometimes clapping after a song, but generally staying silent and still. When Labrie made everyone stand up near the end for Our New World, that's when everything felt right, with most of the people singing along with the music, cheering to the solo and generally having a great time. I ended up having to chase my brother who was going down the stairs at the beginning of Astonishing and we stopped and stayed there for the rest, standing up and singing while most of the people were sitting down again.
All in all, the ending made up for every issue there was that day, and I think they managed to pull off an amazing show after all, especially for it being the third night in a row.