Reflection section is good, you are closer than ever to Katy. I'd say a downside to being in it is that she has her back to RS for nearly the whole of the acoustic section. It's very big, not crowded at all. Usually it's very empty until Katy is due to come on and then it fills up fast!!
People usually have enough room to dance and move around. The only time people stay where they are in RS is when they are at the tip of the triangle, because that's where Katy does most of the interaction.
It's hot, but any concert is. Not squished!
You would get a good view from RS or seats on the side, personally I'd go for RS because it's a great experience! (And you can touch the stage)