I thoroughly enjoyed being in second row GA. For one, you get to be very close to the band of course. I also think it may actually be a better Sphere experience, though I have not seen it from a seat.
You don't get a full view of the screen, but the screen fully envelops your view. You don't see the edges of it or the arena seats, just the band, the stage, and an enormous changing background with no edges. The effect is pretty magical.
You do have to tilt your head way back to see stuff like the ceiling effect during the Fly. If you look closely, you can notice that the area directly behind the band is a a tiny bit pixelated. It doesn't look bad, it's not something you would ever notice unless you were looking for it, but if that may bother you that's something to note. The only other negative I can think of is that the Even Better Than the Real Thing visuals are extremely disorienting if you're looking at the band from GA during the song. If you look up at the screen, it's fine, but you basically have to avoid looking at the stage for that to avoid being sick.