I have read through a few replies and the response to the RS seems to be mixed. Anyhow, I thought I would share my experience. First of all, I will would have to say that if you want the best view overall, that is to see the entire stage spectacle, I would personally say that you should aim for center floor seating, nearest to front row as possible. However, for an up-close, intimate experience, the RS is the way to go. No matter how you look at it, the RS gets you closer to the stage, and provides the best viewing experience for most of the show. But as others previously mentioned, Katy does have her back turned for the acoustic set and portions of some songs. I would estimate about 15-20% of the time she has her back turned to the RS.
I don't know if this is the same for all shows, but the venue I attended had professional videographers positioned around the stage with a live feed displayed on two huge screens. Likewise, the sections of the show where Katy wasn't facing the RS, you were able to look up at the screens to see what was going on, so it was fine.
In terms of best positioning, honestly, I don't know if there was a 'best spot'. She split the show about 50/50 on the main stage and the tip, so it was hard to judge. I would recommend moving around during the concert to find the best place that suits where Katy is performing. I agree with previous comments about the elevated Main Stage, that is to say if you were directly up against the stage, you probably won't see anything due to its height. Standing back a ways is a far better option. However, there are three things should be noted. Firstly, Katy reached out to people the RS at the tip and only a little bit on the Catwalk sides, so if you wish to get a handshake from Katy, the tip would be the best place to do so. Secondly, Katy stopped along the Catwalk for a selfie with someone in the RS, thus finding a spot on the edges would increase your chance of this occurring. Lastly, in regards to questions about fan letters/gifts, from what I saw, Katy only accepted them herself (I assume staff members can forward them for you regardless of seating around the venue) in the RS. If you are wanting to hand Katy something, the best area is the tip of the sides of the Catwalk nearest to the tip. There are a few instances where she gathered fan items, so don't be too stressed if you miss out the first time Katy collects things. All this said, there is plenty of room and not too many people rushed; just find what is best for you!
To sum up, I loved the experience and would recommend it to others. The RS provides a great opportunity for fans, just like any other up-close seating experience a concert provides. However, nothing is perfect and it is all down to opinion, so each to their own, I guess! Have fun!