I have been delaying switching to iPhoto on OSX. A quick experiment had shown that the overhead (actual storage / bare file storage) is too high, although I do not have a concrete number to mention at this time.
Now that I have an iPad, I am stumped by how to get my photos onto the iPad by a simple file copy. Do you have an opinion one way or the other? Did you for instance find a decent way to get your photo library onto the iPad without first handing the photos to iPhoto? Or did you find that the overhead of iPhoto is tolerable in the long run?