I have seen "O" twice, and wonderfully entertaining both times. I think "O" and all Cirque shows (at least the tow others I have seen, Mystere and La Nouba) are better seen from a bit higher up, so you have the ability to be looking down on the myriad of things going on. Also, a lot of things happen up high above the stage area, and if you are down low, you need to be straining your neck looking up, while missing what is happening at that time down low (things are happening everywhere in a Cirque show). Up a bit, your field of vision is more expansive. Also, things happen on the aisle seperating the lower and upper levels, and again, if down low, you need to be looking around to see it, if above, you just look down. And the upper seats are not all that high. Really, all seats at Cirque shows are good, I just like the upper better.
In any case, you will fall in love with it.