I have a Nook Color, Nook Tablet (rooted to Android Honeycomb so I can access more apps) a Kindle Fire, Kindle 3, and an iPhone and iTouch. (I’m a software/hardware junkie. I had an Eris HTC Android phone but the battery life was bad.) I have used and read on the Kindle, Nook, Kobo, and Google Books apps. All work, but the Kindle software wins every time and I find myself always purchasing for the Kindle app because: 1. the sync to last page read always works; not so with Kobo or Nook. 2. Highlights are automatically exported to the Kindle. Amazon.com website where I can review and cut-and-paste from them which helps when quoting for reviews of which I write many; not so with the others. 3. Using Readbility I can instantly send articles I want to read to my Kindle and they appear in the Kindle Cloud and are accessible across all Kindle apps – oh, yes, I often read on my netbook. That’s huge. Can’t do that for Nook or Kobo of Google Books 4. Amazon has hands-down the best search software and the largest database of books.
Kobo and Google Books are improving almost daily. I tried the iBooks store, but it sucks royally. Not even close to any of the others. Nook seems to be static. Ironically, I find reading on my iTouch using the apps. the most appealing as it’s extremely portable and flexible. I have tried the iPad, but it’s too big. The Kindle Fire is great and I like its software. I got my wife a Nook Touch so we could keep our libraries separate (she reads mostly children’s and YA books.) I buy many, many more books now that ebooks are here and am gradually replacing, where possible, my physical collection of 1500 plus with their ebook equivalents.