When I first got my iPad and put a few TV shows and movies on it, I figured 16GB was going to be very limiting. Then I discovered the AirVideo app that lets me stream all of my videos sitting on my computer. I no longer need a lot of storage space as I can just stream whatever I want to watch, even remotely. If I'm ever going on a trip, 16GB is plenty to hold several movies and a dozen or so episodes of TV shows along with my comics and books.
Now my girlfriend, on the other hand, is already wishing that she had purchased a 32GB iPhone instead of the 16GB. She stores everything on her phone as she doesn't have a desktop that is always running and connected to the Internet like I do, just a Macbook Pro that doesn't stay on all the time.