So far I am very happy. I had an iPhone 2G 8 GB and just upgraded to the iPhone 4 16 GB. Currently I have 9.5 GB available still. I have 4 Futurama episodes since I have a pass to Season 7. That is about the only thing that may fill up my iPhone. Plenty of room for all of my photos and the music I want on the go for my use.
Very happy!