I can't fathom people not filling up their iPad. I have a 64 GB new iPad and it's almost full.
Apps 4GB - 1GB from GarageBand, 1 or 2GB of textbooks from Inkling, Zinio etc.
Photos - 0GB (stream instead)
Other - 0.6GB
Free - 10GB.
I've owned my share of 32gb and 64gb iPad 2s and aside from filling it up with movies and music I never watched, I found 16GB is more than enough.
I have 64gb on my iPhone 4S however, mostly because I do benefit from putting all my music, photos, and not worrying about taking videos and photos on the camera. The iPad just doesn't get used for those purposes.
I could also stick a few movies on it if for a trip if I really wanted to.