The concert let me just say this first was a giant production. I don't think I've ever seen anything like it, and it's hard to think about it coherently, rather than as a barrage of sensory impressions.
Reviews have all been positive with caveats. The audience was enthusiastic, and we all enjoyed the show, but the effort of suspension of disbelief may have ultimately been more than they were willing to expend.
The fact remains, they were enthusiastic. We were all enthusiastic. When Miku appeared, we cheered.
I don't have enough information and wasn't seated close enough to do a detailed analysis of the technical aspects of the Miku projection. I can say with some certainty that it was a rear projection onto a semi-transparent, slightly cylindrically-curved screen. It wasn't 3d. Viewers from different angles did not see different images, which was a real problem when she walked across the stage. (But it still looked good.)
When the technology worked, it was brilliant. Miku looked more real than the rest of the band. She was illuminated from within, and she glowed. I think that videos don't really convey the depth and realism of her projection. My notes contain the scribbled comment, "I didn't realize we were going to see Sharon Apple".
I don't have a lot to say about the music. You've heard Miku, I'm sure. She doesn't sound quite like a person, but it's close. For some people it's squarely in the uncanny valley. For others it's made of pure Moe. Some days I'm in one camp, some days in the other. For the space of the concert, though, Miku was there. Pitch-perfect, and not at all robotic. I loved the costume changes, I enjoyed hearing these songs again, but they're kind of forgettable pop. I forgive them that.
And it was nice seeing these songs performed live. Literally performed. People tend to elide this in their reviews, but Miku had an entire band, a crew of talented musicians. The band was good too very elaborate, very professional. Unfortunately somewhat upstaged. They also introduce a slightly more subtle problem. The band makes it too obvious that it's all scripted. When Miku introduced them all, it was brilliant but limited. I can't quantify or even positively identify spontaneity, but surely it's got some value, and everyone agreed it wasn't there. That was the common thread through the reviews. People liked the show, but it ultimately felt incomplete, like it wasn't a live show at all.
And that's a real pity. But we have confidence. One day they'll be able to do it in real time. And Sharon Apple will once again walk the earth.