mattwnz: Isn't 16GB going to be too small, as retina display aps are going to be huge in the future. You are going to get apps that are 1GB in size easily. I have already got several 500MB apps on my ipad, and they aren't retina supported.
It depends what you do with it, I currently use 5.6GB of space on mine. My iPhone is where I store my music/photos etc so I only need it for apps.