Saw this earlier in the week. I liked it enormously, but it did not reach 'love' status for me.
First and foremost, I thought that Darren Criss gave a phenomenal performance. I was unable to see Jonathan Groff (I have to wait until October), so I will only say here that to me his performance merits a Tony, whether he gets one or not. Some people have posted that his singing is not that great. All I can say is that it was more than up to the songs he had to sing. His balancing of the human vs. the robotic was amazing to me. Helen J Shen was also wonderful, although Criss is clearly the lead. I can understand why she did not receive a Tony nomination in this particularly strong season, but she was terrific and I doubt that her performance could be bettered.
The book was extremely effective at juggling the sweet and innocent with the deeper issues about mortality...so damn clever and able to get you to care so much, despite being reminded constantly that they were robots. The production design and staging were stellar, particularly in the firefly scene, which was positively beautiful. My only complaint is with Arden's ignoring side seats with some of his decisions. I was in a seat 4 or 5 off the aisle, not yet in the middle of the side row (about 12th or 13th row) and did not see the left side of Criss's room. Not a big deal, but I wondered how much people further to the side were missing. It wasn't necessary, he is smart enough and creative enough to have avoided the problem. Were I a Tony voter, this would have been a negative factor in my decision making on who to vote for. Truthfully, however, I would still have voted for Jamie Lloyd (although I expect Arden to win).
The think that kept me from loving this is that I did not think there was a single song that stood out. All the music was fine, but it wasn't great. Of course, that is more the norm nowadays, unfortunately.