I want my iPad to be a tool as well as a toy. I downloaded Portfolio and am pleased so far. I know I can customized it to my branding if I was ever to use this to show clients work. Right now I am using it as a place to put all the patterns I am working on. Monday I am meeting with my artist's group and this is an easy way to show them what I am working on.
I upload all my files from my computer to DropBox and then in Dropbox on my iPad I download into Portfolio and Bob's Your Uncle.
I think it was $14.99. It is robust and a good organizational tool so I think it is well worth it.