For me, it was always the portability of it that intrigued me. I was tired of toting around my 13" MBP all the time. To date, I have sold my 32GB iPod Touch and my 13" MBP. Time will tell if I will/can sell my Kindle too.
I can see where having all of them is nice, but like I said, for me it was about cutting down on my daily carries. My handbag was too heavy and cramped.