Just checked my iPhone storage and just under 30GB at the moment. Because of Retina screens iPad/iPhone apps have grown greatly in size. Therefore I find that if I don't want to be spending half my time balancing the contents of my devices I buy larger storage devices.
On my new Retina iPad I have only synched around 80 of my most used apps and already I am at 36GB used up. That doesn't include any music, videos, photos or books (some of my multimedia books are a few GB in size). My apps include games, flying, office, navigation, photography, videography, music, eduction, medical, autism, sign language and medical. I also evaluate apps for my school so tend to have a few different variations on to compare at any one time.
I have loads of video clips to add to the iPad rMini once I sort them using iFlicks and the same with books and a host of PDF files, which I will sort out with the new Mac iBooks app.
Obviously everybody has different needs but we certainly find it extremely challenging to manage our 16Gb iPads in school. They are only non retina iPad 2s but the apps are still retina playable so larger than we actually need. We are forever having to make choices between really good content. Managing it is crazy when you are near the limit as you can't synch if you have not got enough free space, even though you appear to have room.
My advice to any would be buyer is to think very carefully about what you want to use your iPad for before deciding on a storage size.
