Ive had Sony Readers for a few years and enjoyed them........... BUT my Kindle 3 is pure love. I adore this thing!!!
My Sony allowed me to read ebooks, end of story........
My Kindle makes it fun ! My Sony was only as fun as the book I was reading on it, the Kindle is fun even when your not reading and just browsing or playing
I love everything, the store, the samples, the search functions, the keyboard, the collections being accessed while on the kindle, the screen, the wireless delivery of books from Amazon and Calibre, sending newspapers to my kindle. All that and its mega cute too

I can't ever see me being kindle-less now, not ever, I love it way too much to part with it.