I was in the lower levels, and there were times that I heard the synth buzz, but it wasn't bad.
I'd have to agree with you on all points, especially with the Cadets. I really enjoyed their show, which is great to say because I was never a fan of their narration (And therefore I didn't really like a lot of their shows in the mid-late 00s). I didn't necessarily like the recorded music at the beginning, but there's a certain amount of give and take, I suppose. It wasn't playing when the judging started, so it was just for the "warm-up" time.
And I definitely agree about the Blue Devils not fully utilizing their musical talents. The show was last night and I honestly cannot recall what they played, or even what the tone of the show was. It was just sound. In tune, and sounded great, but I just remember that there WAS music. I think they could do a lot more musically.
As for SCV, One moment REALLY stuck out to me... right near the beginning, the corps turned around, and the trumpets came in, and it sounded SO GOOD. I was REALLY impressed.
That's all that I have to add :)